keep the following in mind:
Permissions (what user accounts on your computer are allowed to access, edit, etc. various files) differ from person to person, but if you ever enter a command and get a message that you're not allowed or don't have permission to run that command, try entering the same command except prefaced with the word sudo plus a space. If the command xcode-select -install returned a message that you don't have permission to execute that command, for example, you would instead try entering sudo xcode-select -install. Type your computer's password and press enter when prompted to do so. (This lets your computer know you have permission to execute this code.) In general, permission defaults are around for a purpose, and a lot of permissions are tied to the root/admin user to make them hard for anyone not sure what they do to accidentally open their computer to risks, but it should be safe to use sudo for any command in this lesson.