It depends on the relationship between the items. Is it a specific unique item in the level? Is it listed in the AI Perception, or Box Trigger Volume? Are you standing close to it, and looking at it?
A common way for this last option, is to cast a single line trace, from the camera (so you can use your crosshairs to be accurate), and then use the Hit Actor output, to get the reference to item you need. From there, you can change any variables you want (within the actor).
Fortunately, Unreal have the documentation to do exactly this here, nice and quickly. (Using a Single Line Trace (Raycast) by Channel | Unreal Engine Documentation)
The only thing I would change is use a keypress event, rather than EventTick. They just use Event Tick to better demonstrate the result of the line trace.