Hello,
If you mean how do you change what the AI does, what it builds, etc. Then you need to start playing around with the SLIC code which determines what the AI does.
There are several mods about which have already altered the SLIC code to make the game harder, etc, such as AIfrenzy, which I have just downloaded and would highly recommend.
As to actually playing about with the SLIC code I would aks about it the mod making section of the CTP2 forums. I'm sure some SLIC vet would be happy to help.