Powering APM 2.5 using Power Module

I have been trying to understand how to use the power module from the link supplied above but so far no joy.

I plug it in and nothing happens.
I plug 2 becs into the output side (as intructed) and still nothing happens.

The only way I could access the optional frmware for the module sttng was via mavlink

First of all, did you purchase your PM from 3DR or is it a clone?
If it is a clone, many of the clones are not a complete PM and will not power the APM so we cannot help you here.
Also, is your APM a genuine 3DR product or a clone?

Its says Arducopter on the case.

A genuine 3DR APM2.5 says “Ardupilot” on the case and not “Arducopter”. I suspect that you have clone parts. Who did you purchase your APM/PM from? If they are clones, I suggest that you refer to the seller who sold them to you or the manufacturer of the clone parts.

am I correct in that the only way I can access the battery module setup is thro mavlink?