I run my extension cord from the pedestal to inside the trailer through the same hole that my camper electric cord passes through. From the inside I have easy access to the space where the cord wraps up inside the camper so it's really easy to just pull the cord right on through and I can use it anywhere in the camper that way.
On my previous camper I ran an extension cord through the window I just popped the screen out slightly and then could pass the extension cord through that way.
On yet another camper I ran an extension cord through the pass-through and it would come out from underneath the bed and then I could put it anywhere inside camper I needed.