Ok, great that you managed to find a solution, at least. Hope you’ll figure out exactly why it worked as well 
I’m not entirely sure what you say when you say “this blueprint itself” do you mean the one in my screenshot? That is indeed from the level blueprint. I do not generally use the level blueprint except for testing something out really quick. You can ignore most of what is in the blueprint above. The important part is the attach to component node. The rest is just to get a reference to a suitable actor.
From a high level perspective I guess it depends on your game. If you have an inventory screen you would probably do this from the blueprint you have created for managing the inventory. Possibly some form of equip event contained in your pawns that an inventory blueprint can call. I would probably do something like that myself, at least.
For equipping multiple weapons on multiple pawns you would need to get references to each pawn and do the same thing for each.