Question about Gold AI

[Madmarlin]

So I purchased the gold Version, and installed the TDM mod and I enjoy it quite a bit. Thank you for encouraging me to buy the gold Version.
My new question is this: After reading which AI races are the most challenging I set them up as players in the game, but they are all set to human players. How do you pick which races to be in the game as computer controlled? I could have just played one turn as them being human, then cliked on the player tab and set them to computer, but this doesnt seem to be the optimal way.
How exactly do you pick races to be computer controlled to your new game?

Thanks
MM