Yeah the AP has to be factory wired.
Basically the DC Jack inside the AP has to be connected to two unused pins in the RJ-45 Jack.
I would suggest using POE AP only with the brand counter part, otherwise you take the risk of frying your NIC, or AP.
There is a cheap way to do home made POE without touching the AP, but I need time, and the capacity to post pictures in order to explain how to do so.