Shooting a weapon after it's equipped

I put in a cast to my Weapon BP (parent class) and I tried to get the “Fire Gun” event from it but it would only show if I disabled “Context Sensitive” in the search menu. I also don’t know how to set the “Gun” variable to the weapon picked up and my code has no way of telling which child class the weapon picked up is. Also how do I set references? I’ve typed in the search bar for them but nothing comes up.
Here’s the code snippet I have at the end of my equip code: