How do you tell your friends that you can sing?

Me and my mates are the type of people who are never serious and we all ways like joking around singing really badly, but I have sung in front of thousands of people on stage before and have been in many choirs taking solos and lots of people who have watched me perform have said I'm really good I want to tell my friends cos they all think that I have no real talents but I don't know how to tell them.