HELP: How to make 2 objects rotate around themselves

Hello I am wanting a little bit of help in Xcode to code and make two objects or images rotate around the other.

example. for a basic start I would like 2 circles. cirOne and cirTwo and code cirTwo to circle around or orbit cirOne when the screen is tapped. Ideally would like cirTwo to rotate around cirOne indefinitely until the screen is tapped again.