How do you actually connect the Ethernet cable at the back of the module?

The installation cable terminates directly onto the IDC contacts at the rear of the RJ45 module. You lay the individual conductors into the colour-coded positions and punch them down; there is no RJ45 plug on that end.

The first attempt can look like a small nest of coloured conductors, but the markings make much more sense once the pairs are actually in front of you.