Here are some good diagrams from Lenz to show how to hook-up a reversing look module.
The basic hook-up method:
This is interesting. You can keep all the yards and stations the same polarity and reverse the polarity on the mainline loop. This prevents having to install reversing sections between the mainlines within the station and goods yard areas:
Wye reversing section. Less common on British layouts though:
Turntable implementation. This also need a reversing module as the loco is swinging around and you want to drive on and off without switching direction on the controller: