How do I print on mac, when needing a printer administrator I'm trying to print something with my Macbook air, but when I try to print I have to add a printer. When I try to add a printer it asks for a username and a password of some user in the printer administration. How do I solve this?
If it's your macbook, usually YOU are the administrator.  Try using your own username and password.

I don't remember my username and password

Click the Apple (grey, upper left) 
 =>System Preferences
 => Users and Groups

Your name should be highlighted.  You can change your password here.

It will also say if your account is standard or has admin rights.