How do I prune grapevines?

[KatherineA]

I purchased a home with some well established grapevines in July. The grapevines are beautiful, but I learned they should have been pruned in late winter. I wonder, is it too late to prune them now? Does anyone know a good resource for learning how to prune grapevines? I have found brief instructions on the internet, but I don't quite understand how to do it. I will likely just enjoy their greenery this year and hopefully by next winter I will have learned how to prune them and can enjoy some fresh grapes!

Any guidance anyone can offer is appreciated. Thanks!