Did you take a look at the example map that came with the pack? Just look at how its set up there. But here is an explanation.
Set up ur lift walls on ur 3 levels. Then add a floor and ceiling to each. On each floor of each level put the corrisponding lift(the plate looking things that say "lift1" "lift2" etc.) Add ur floor select buttons, and ur lift call buttons. Each lift call button is set up the same way as a remote door.(right click the floor select button and put the name of the door its controlling in the "if used" feild.
If my explanation was a little confusing just open up the example map and look at the lifts. That along with my ramblings and you should get the idea.
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