i have an engine and a body now what
 

I have a 13B-RE-90-95 JC cosmo Twin Turbo J-spec engine i got from fc3s.com i just found a 3d gen 1995 RX7 body for 1500, i currently drive an 88 NA what else do I need to do so I can drop the jspec into the body and drive it. also why cant i get into the rx7 chat it says its forbidden for me.

You found an FD body for $1500? Where? Was it burnt? Maybe you left off a "0"

As far as putting the Jspec in: yes just pull everything off the Jspec and put/drop it in, putting everything (such as sensors, electrical, etc) that was on the old motor onto the Jspec.