First time owning a civic tried install a single din deck but got no power checked and replaced the 7.5 back up and the 10 fuse tested the wires with a pen tester and it only lit up on one of the speaker wires is my wiring bad

 

Its quite possible and fairly common to have a break in the wires going to the speakers. Many times its at the door jam area since the wire is constantly flexed there for decades.

 

So I need to just check the wires at the door jam to see if there's a break

 

Not necessarily, I don't remember off hand if there is a connector in between the speaker in the door and the head unit in the dash. If there is, then there is two sections to continuity (ohm) test. If not then you get to test from the speaker to the head unit.

The speaker wires are rather a pain in the harness in the route from the door to the head unit. Most people tend to run fresh wire outside of the harness. To fix properly (if their is a break) you tend to have to pull the dashboard out so you can dismantle the cabin harness.