Invite friends in application

Hello guys!

I'm new to the community and i hope i'm not posting in the wrong section of the forum.

I'm developing a small fantasy football game for a university project.

In my application i would like to add an "invite friends" section to invite friends who already have the app to participate, for example, in a tournament the user creates.

Can someone give me a hand or suggestions? It would be wonderful if you even have examples on how to do it.

I'm really struggling over this :(

Thank You very Much

Luca