[Need Help] Custom Hero Pool Selection

Hi Guys, I'm new to Modding, so please be patient with me :) I've just recently played with the development tools and still don't know how to limit the hero selection pool. (I only want players to choose from a pool of 20 heroes at the start of the game)

Help :{

TAKING IN SPELL REQUESTS (Not too advanced). PM ME if you need help. https://moddota.com/forums/profile/4159/Rubician