Ableton Forum

How would I use hardware instruments or effects like the Kp3 with ableton live?

Well, uh, you plug in some cables to your interface, change some routing, and get to work.
Your question is pretty general. Can you make it more specific? Like, what exactly are you trying to do?

try searching either

1) the forum
2) the manual
3) Google

before someone gives you a valid answer you can find it for yourself