I am trying to make a set of Armor that makes the AC = 10 + Charisma Mod. 

Any idea how to do this? 

Start with leather armor and add the following Modifier to it:

• Modifier: Bonus->Subtype: Armored Armor Class->Ability: Cha->Fixed Value: -1

That will however still include the character’s Dex modifier too. If you want it to not also include Dex you would have to add the following Modifier to it:

• Modifier: Set->Subtype: AC Max Dex Armor Modifier->Fixed Value: 0