snapchat update problem

when i want to update my snapchat i cant because appears icloud uncle

When you use your uncle iPhone, your uncle need to read -> this Apple article: What to do before you sell, give away, or trade in your iPhone, iPad, or iPod touch

What to do before you sell, give away, or trade in your iPhone or iPad - Apple Support

Then he has to remove the iPhone from his account, see this Apple article: Check your Apple ID device list to see where you're signed in -> Check your Apple ID device list to find where you're signed in - Apple Support

Then you can sign in with your own Apple ID.