From the videos I am seeing on youtube the bushing goes inside of the larger piper and the smaller pipe goes inside the bushing, both glued which I like more than using a rubber gasket It also seem to save room compared with the reducing coupler that is longerWho told you that?
I expect that is made to go into a 2 inch hub, and accept a 1.5 inch pipe. You have the equivalent of a 2 inch pipe coming down from the drain, right? So you would need a 2 inch coupling (two hubs)plus the bushing
Then a short length of pipe into the trap.