I'm new too, but recompiling is easy.
1. Go to your Halo CE directory. "C:\Program Files\Microsoft Games\Halo Custom Edition" for me.
2. Find and open tool.
2 1/2. Type "tool" and hit enter to find a list of comnands. <<<--- OPTIONAL
3. Type: "tool build-cache-file levels\test\<NAME OF MAP YOUR REBUILDING>\<MAP NAME AGAIN>" and hit enter. Wait about 5 minutes tops, and voila!
P.S. Take out the " before hitting enter.
Replace the < and > and the text inside it with the map name.
Also, if this is a bump, sorry.
PM if having problems.