I planted 2 seedless grapes, Niagara and Concord, on 2 pillars about 10 feet apart earlier this spring.

They are growing a lot, and the Niagara has branches trailing on the ground.

How should I prune/train them this season? I can run wires between the two pillars if needed, and I may plant a third grape between them because I have plenty of vertical space and I could maybe train the center grapevine much taller or shorter than the other two.

So what should I do for them this season?