Without any specifics I'm not sure how much I can help you, other than to state the obvious that the proper way to format the file is to follow the same formatting as the provided ini.

What were you trying to change? What did you do? What went wrong?

Thank you so much for the reply.
Ok, so I was trying to change up the abilities that the psionically gifted soldiers have access to by adding more abilities to the +AllowedPsiAbilities and adding more to the three the "+PsiAbilities = (AbilityList..." things.
One of the things I also did was lengthen the three +PsiAbilities lists and added abilities like Null Lance, which showed up as a missing location description or something.
What also ended up happening is that in-game, whenever I selected eligible soldiers to be trained, the abilities I selected were not the ones that they were eventually given. Like the buttons correlated to the wrong abilites than the ones shown.
Additionally, this happens regardless, but the prompt asking if I'd like this soldier to undergo psi training for every ability shows up.

By default ya got this setup in the INI:

+AllowedPsiAbilities = "Soulfire"
+AllowedPsiAbilities = "Insanity"
+AllowedPsiAbilities = "Stasis"
+AllowedPsiAbilities = "Inspire"
+AllowedPsiAbilities = "Fuse"
+AllowedPsiAbilities = "Solace"
+AllowedPsiAbilities = "Fortress"
+AllowedPsiAbilities = "Sustain"

+PsiAbilities = (AbilityList = ("Soulfire", "Insanity", "Stasis", "Fuse", "Inspire", "Solace"))
+PsiAbilities = (AbilityList = ("Insanity", "Stasis", "Inspire", "Soulfire", "Solace", "Fortress"))
+PsiAbilities = (AbilityList = ("Soulfire", "Insanity", "Fuse", "Stasis", "Inspire", "Sustain"))

I simply added a few abilities to the allowed abilities above, then added them to the ability list. This exasperated the problems I listed above further.
I guess I'm asking what should be done if I want to increase the number of abilities available, and where I'd put them.
---- Sorry if I am kinda spamming, but I appreciate the feedback! ----

If you're getting a missing location description and there's no icon, then you've probably put in an ability that doesn't actually exist, and that's going to throw everything off, which might explain your other problems.

I should also warn you that I only ever tested it for 6 abilities, so it could be that there's something that just makes it not work if you have more. I'm not really sure what it could be, but I haven't delved into it, and, to be perfectly honest, I'm not going to; I'm not really interested in spending any time testing it because I'm pretty happy with the mod the way it is.

Hmm, ok, appreciate the reply regardless. I ended up re-installing the mod and NOT touching the config (lol) and it works fine. So thanks again :)