How to Cast discharge? - SpellCaster Perks Questions?

Ok guys, I was having the same issue and I actually worked it out so thought I would update you in case you still need help and made the same mistake as me.
When you look at your spell caster skill tree there are actually two skills that mention using discharge, The first skill you see (mentions charging and discharging)- but it does not actually give you discharge. You will need the skill two columns across that only mentions discharge. Once you have this skill then you click on you character- magic and discharge will appear. as for using it in the magic realm I was there when I used it so I am not sure yet if I can use it outside. But the first column tree only advise you have more power for charge and discharge in the magic realm.

I was honestly so frustrated trying to get it to discharge and a little disappointed it won't discharge over time (I waited two days) I almost forced my character to kill herself so I could revive her without the charge and just as I order her to use magic I saw the problem.

Yeah, there's a few different perks relating to charge. The third stage of Prowess is Charge Control, which allows you to use less charge. The one you want is Discharge, the first Spellcasting stage; the second, Power Shunt, is also useful (it's similar to Charge Control).

Also, can confirm that you don't have to be in the Realm. This is in Jamie's basement in Brindleton Bay.

https://i.imgur.com/tftlAQO.png