The Bridge/AP should ONLY be powered via Ethernet cable connected to the included PoE Injector.
You should connect the cable to the PC's router. If your Computer is already on a network, ensure that you have set it to a Static IP Address on the interface.
Example: 192.168.1.10 and the Subnet Mask address as 255.255.255.0.
The above is an example. You may have a different address. What is the address you use to log into the router?