Can anyone give me a link that will teach me how to prune a grape vine?

3 years ago I decided to try a domestic grape since the wild ones seem to do so well, even when I don't want them too. I got a Niagra from the nursery and it is doing wonderful, now has a spread of over 20 feet and is putting on it's first crop of grapes, quite a few bunches.

Seeing as that it's doing so well, I want another, a purple one, still up in the air as to what kind.

Thing is, my husband, for some reason, does not want me to make a grape arbor, even though we have everything we need as far as structure and space, and doesn't want me to start on another part of the pasture fence. He wants me to plant next to the one I have, which is only a ten foot spot on either side.

So I have to see it I can prune the one I have and still get grapes, give up the whole idea, or try to talk the hubby into letting me use another area.

Thanks for any help.

Now, a little bragging, I'm proud of my grape. Here's the vine.

And Yea, grapes, these are just a couple, I have a good dozen bunches starting.

PS, don't mind the spots on the leave, I'm totally organic and don't need the leaves to look perfect as long as the vine is going great.