I forgot to list the plant names in the previous message. The following is the list, so you would have an idea what kind of soil those plants like:
White Yarrow
Cornflower
Siberian Wallflower
Garland Chrysanthemum
Ox-Eye Daisy
Plains Coreopsis
Wild Cosmos
Sulphur Cosmos
Sweet William
African Daisy
California Poppy
Perennial Blanketflower
Annual Indian Blanket
Annual Baby's Breath
Baby Snapdragon
Blue Flax
Sweet Alyssum
Bird's Foot Trefoil
Evening Primrose
Red Poppy
Rocky Mountain Penstemon
Yellow Prairie Coneflower
Gloriosa Daisy
Black-eyed Susan
None-so-Pretty (Silene armeria)

Organic material is the best thing to add in now without going in and disturbing the soil (tilling up the hillside). If you're willing to till up the area, all kinds of things are possible, but I'm guessing that is not what you intended.

Shredded leaves, grass clippings, wood chips, compost. Not too thick a layer at any time if you're trying to grow seeds. If they have already sprouted and are growing, you could sprinkle a thicker layer around the plants.

Adding organic material is the best way to improve clay soil. It will take several years to see a change and require annual additions of more organic material forever to maintain the change.

The better solution for an area that you want to be low maintenance is to only plant things that are suited to clay. It is much easier to select plants for your conditions than to change the conditions.

BTW, many of the plants on your list are not native. Is it one of the "wildflowers in a can" mixes? Planting a large area with perennials by seed takes careful preparation including using a cover crop like annual rye to prevent unwanted weeds while the perennials take.

See the link below to Prairie Moon Nursery. Their seed catalogue includes detailed directions for planting a meadow or prairie. They also have a seed mix suitable for clay (they call it wet-mesic) and are available by toll free phone for consulting. They will custom blend a mix to suit your conditions.

Here is a link that might be useful: Prairie Moon

Thank you all. Well,, The seeds are from American Meadows Co. They have a web site that I can click on the region, so I thought that the seeds from for the south east region, which I chose (GA). Well, all your advice is all very helpful. Thank you

American Meadow also lists their seeds by individual plant, you may be able to exchange your mix for some of the individual packets.

Do not get any that need a loose soil, a gritty soil or dry soil or that are native to desert areas. They will not do well in clay.

Here is a link that might be useful: Individual Seeds

You might look at the catalogue for Prairie Nursery in Wisconsin in the link below. They have native plants especially for heavy clay -- their 'Clay Busters.' They also have instructions for clearing and seeding, not an easy job.

If you just toss seeds in the area, you run the risk that the weeds in the soil already will strangle them and take over again. Otherwise, what everyone else says about amending clay soil is right -- lots of compost and other organic matter.

Here is a link that might be useful: Prairie Nursery

I completely agree that it is a lot easier to select plants that will tolerate the conditions than it is to change the conditions on the hillside. However, some cut banks have newly exposed clay that might not support much vegetation for a number of years while natural processes slowly change a clay subsoil into a clay soil that can support plants. If this is the case, then you might need to do something to the soil to make planting wildflowers - even wildflowers adapted to clay - feasible. I would consider planting a cover crop. This would be a fast growing ANNUAL crop that will create lots of organic matter, break up the soil with its roots, then die. Oats are popular for this. Annual rye grass is too, but make sure you plant only annual rye, not perennial rye. You might need to break up or at least scratch the surface of the soil before you sow the seeds. I would plant the oats really thickly. For color you could add a few sunflowers to the oats - just use sunflower seed sold for feeding wild birds. Don't plant any perennial plants. If you ask around, you'll get lots of recommendations for perennial plants to cover slopes, and some of these would probably grow, but they would keep growing ifor years and prevent you from eventually planting wildlfowers.

If the oats grow well this summer, next spring you can plant wildflower seeds into the dead oats. I'd select species that are native, tolerate clay, and you like. I would not plant any "wildflower" seed mix. Most of the seeds in mixes are not native, and many won't be well adapted for your hill. I think picking out species is the best part of the process and will entertain you over the winter. There are lots of websites that describe wildflowers and how to grow them. I usually try to compare several websites or books decribing each plant to make sure I know a little about each plant before I try to grow it. You can expect despite careful planning that some of the plants you select will thrive, while others won't grow well, This can't be avoided. Eventually you'll know what grows well and looks good on your hillside, but it will take a few years. If there are similar slopes in the area, check out what grows on them this summer for ideas. Expect that most of the plants along a road or behind a building will be non-n ative weeds you wouldn't want to plant, but a few will be natives.

Thank you all so very much. I have a direction to go for now. :-)