here is a quick video that explains a few things
https://www.youtube.com/watch?v=7uS9gvGHH6U
another which shows with engine running
https://www.youtube.com/watch?v=U1GgQ-3asJQ
those vac pumps are actually pretty cheap and come in handy for bleeding brakes and all sorts of other things around the shop. try to get one with the little canister for collecting fluid before it gets to the pump.