Token mod for Faerie Fire (Shaped 5E)?

How would you use token mod to set this spell?   I will put a button in the spell that I can click and it will allow me to select all the targets of the spell which will then call for them to make a DEX SAVE or cause them to have an AURA of blue out to a 10' radius and also emit dim light.  Is that doable?  If so, how would you go about making it happen? Would I need to use Groupcheck?  Has anyone done anything like this already??

I don't think anything like this exists. TokenMod can certainly give all selected tokens the aura and light, but it doesn't do the Dex save. GroupCheck+ApplyDamage can give all those tokens who fail a status marker, but it won't apply aura+light. The easiest way I could think of (mostly because I wrote it, I guess) would be to extend ApplyDamage to add features to set an aura and light.

Tell me about apply damage.  How does it work?  Is it easy to use (for a non programmer)?  Will it adjust the HP bar after the fireball goes off?

Yeah, you just install it on top of GroupCheck and make a macro. I've provided an example macro in the GroupCheck thread, let's assume you use that (it's all you will ever need unless you want to add status marker stuff). You select the tokens, press macro button, it will query for type of saving throw, DC, and damage. Then it displays the saving throws in chat, and below them, a button you can click to adjust HP bars accordingly.