First you have to dig or till the area you want to plant very well so you have loose soil. Then you have to amend the soil with compost or good soil.

I don't think they sell corn that's started. No it is not too late to plant corn from seed if you get the right variety. Ours won't go in for 3 weeks yet and we always have corn

We usually grow a variety of SE--(sugar enhanced) bicolor (peaches and cream)called Fleet. It has an early maturity date for our zone 3 climate and a sweet tender flavor. If you can't get that variety look for a peaches and cream variety. They are usually a good corn.

Each variety has a maturity date and it is usually marked on the package. It can be anywhere from 60 to 90 days so choose one that will grow to maturity in your climate.

Corn should be planted in multiple rows for the best pollination so plant 2 rows in your space and not one long row. It needs regular watering and the easiest way to do this is to lay the hose at the far end of the row and between the 2 rows of corn. Then turn it on half way and let the water run with no nozzle. Every 10 minutes or so drag the hose up the row to a dry spot and repeat. This get the moisture to where it's needed at the roots

I hope you get a good crop

Just a few more details about corn pollination you may want to know someday. Many corn hybrids can cross pollinate. If you have corn farmers in your area, their corn may be able to pollinate yours and vise versa. Cross pollination, for some hybrids, can impact flavor, etc. To learn more, do a web search for "Sweet Corn Genotypes". One of the reasons to plant corn in a square instead of one long thin row is to minimize cross pollination.

I have seen it written that "sweet corn must be isolated from field corn and pop corn". If you don't have any corn farmers across the street, your probably ok. Corn seems to be a science in itself, but there are plenty of people that grow great sweet corn!

Sweet corn needs warm soil, so you are not too late (might actually be a lil early). They sell transplants around here, so they might do the same up there (or you can try to sprout them yourself).

Go with a short season variety (Ruby Queen or Bodacious).

Feed n water. Corn likes to be fertilized...especially nitrogen.

"Growing Your Own" (Oregon State Univ Extension Service) is helpful for all gardeners. You'll find the planting chart (page 7) particularly useful --
http://ir.library.oregonstate.edu/xmlui/handle/1957/21092

And here's the most recently published "Vegetable Trials" from OSU -- http://ir.library.oregonstate.edu/xmlui/handle/1957/21092

Here is a link that might be useful: Growing Your Own

What type of soil do you have?

Corn is grass, how well does your grass grow?

In a six by twenty area it would be better to plant multiple short rows the short way and space the rows two-feet apart.
Space the kernels six to eight inches apart. It is not necessary to put two kernels to a drill, or you can dig a shallow trench, one and one-half inches deep lay them on the bottom and cover.

I finished planting my corn last week but this is earlier than normal in Minn.
I have planted as late as the first week in June.

Depending on how sweet and how much old style corn taste you prefer will determine which type to plant.

I have planted multiple types of sweet corn with only three feet separating types.
I have never had problems with crossing,(I also plant field corn in the same area at the same time but pay attention to when types come ripe).
You should not have to worry about cross pollination as I have never has sweet corn go bad.