[Help] GroupInitative - Setting up custom initiatives

Hi there, I'm too small brained to understand or successfully search how to set up custom initiatives for some of my characters. I've got the whole stat-dnd dexterity thing going, but I've also got a player who is playing a War Magic Wizard that adds a bonus to their initiative based on their intelligence modifier. And then another one playing a Lore Mastery Wizard that lets them choose their intelligence modifier as their initiative. Who knows, maybe someone will get the Alert feat that gives them a +5 bonus initiative. So I basically have no idea how to make it so all of that applies when I click my group initiative macro button, even though it's MOST LIKELY there in the description of GroupInitiative on how to do it. Again, me low int orc. :( Any help would be very appreciated. Thank you.

Probably the easiest thing to do is create a stat group for your normal rolls, then create a rule that uses a custom attribute and promote it to the first rule. In the custom attribute, you can add references to the attributes that matter for that character. The rule will get skipped for all characters without the attribute. 

Which 5e character sheet are you using, Diceykins?