if you wanna implement a simple pick up system there are two options
1- using overlapping: add a sphere/box collision around your character and say if a key is pressed get all overlapping actors which gives you an array of all actors inside that collision then cast them to your pick up actor class if cast succeeds you can add them to your inventory.
2- ray tracing. which traces a ray toward your camera direction and gives you the hit actor.
why don’t you google for it?
google this: UE4 simple pickup system :))