A few pointers in case anyone else is wondering too:

• Global Settings | AI Options, make sure to choose Fuzzy AI.

• If you want to create your own AI templates, have a look at Fuzzy AI documentation.  Don't worry if you don't understand everything straight away, but it should give you a good base to start from.

• If you're happy to use the provided templates, then you can just add the appropriate ones to your characters (Rushdown templates for your rushdown characters, Grappler templates on your grapplers etc).

• I assume your specific question is about automatically assigning the AI instead of choosing it at the character select screen?  Have a look at CharacterSelectionScript.cs, that gives an example of it.  Basically, you just want to call the below when your user selects "Arcade Mode" or similar:

UFE.SetCPU(2, true);