Two way gaming live stream HELP

Not used twitch before but needing some advice.

I will be having two people gaming simultaneously on separate machines. I want them to output to me, guess via a capture card of somewhat, so I can then vision mix it and out put it to twitch.

How can I make this happen?

This forum is for third party developer support for the Twitch platform. If you need help with streaming, I would try /r/Twitch or the forums for your broadcasting software.