Ok, so this script, which was made in the character blueprint, makes it so that when I press the left mouse button, I throw a grenade, which destroys itself within a set amount of time:
The “Add Grenade Ability” node or function that you see there, houses this:
Then the SpawnActor Grenade node is linked to this Blueprint Class, which is an actor:
However, what I want to do is to have my grenade throwing abilities disabled at the start of the game. My grenade throwing abilities, I want it to be enabled when I hit a trigger. Hope that makes sense 
So I guess for this to work, I need to figure out how to set the value of that boolean variable when I hit a trigger. But how do I do that?