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.
In macOS the user account has to be member of the admin group to make system-wide changes, adding printers is one such change. However, if you want to give a specific standard (non-admin) user the ability to add printers without supplying administrator credentials, you can include the user account in the _lpadmin group. Type following in Terminal, replacing someuser with account name you want to change:
sudo dseditgroup -o edit -a someuser _lpadmin
If you want to extend that right to all standard users on the system who are all members of the group staff, you can include group staff to the _lpadmin group. Type following in Terminal:
sudo dseditgroup -o edit -t group -a staff _lpadmin
Since the Terminal command is prefixed with sudo that means that you will have to enter administrator credentials to make changes to the user database, but any subsequent printer administration by the standard users will not need administration credentials.
If you are in a controlled enterprise environment and do not have administration rights on your computer then ask your IT department to make the change to include your standard account in the _lpadmin group on the Mac.