I use alligator clips with speaker wire attached to the cabinet speaker. I loosen the cabinet speaker and feed the speaker wire under the speaker out of the cabinet. As far as hooking up to the sub, it seems to depend on what sub you buy. The polk psw10 hooks up just by putting the speaker wire in the red and black inputs. The Monoprice 12” sub I just bought was more difficult and there is a full thread on it.
https://pinside.com/pinball/forum/topic/12-150w-monoprice-sub-79-free-shipping