How do I claim fortnite keys?

Excuse me, I'm having some trouble understanding how to go about claiming my Fortnite keys. Could you please walk me through the process step-by-step? Are there any specific requirements or prerequisites that I need to meet before I can make a claim? Also, how long does it usually take for the keys to be credited to my account after I've completed the necessary steps? Any information you can provide would be greatly appreciated.