How to Fire a Event when a button is clicked ?

Thanks for the reply, actually i did watch a lot of tutorials but majority of the people are making the same tutorial, same thing different person for example " pickup items " just to name one and you’re right this could be a more in interesting thread only if people share there knowledge with newbie like myself. I have a great portion of my game ready but currently stuck in tree obstacle which are
1). Switching weapon through a button in my HUD instead of using numbers keys
2). Unlocking a inventory slot when a person purchase the item
3). How to establish a InApp-Purchase feature

If you know about a good tutorial or documentation on how to accomplish this please point it out. Maybe the solution is out there but with my lack of knowledge i can’t wrap my head around it that why im here looking for help, guidance, blueprint example from expert who know how to achieve this.