User Self Service
With self service on, anyone who can reach your Pinepods sign-in page can create their own account.
Turn it on under Settings → Admin → User Self Service Settings → Enable User Self Service. The sign-in page then shows Create New User, which opens a form for a username, full name, email and password. The new account is a normal user, not an admin, and can sign in straight away.
With it off, only admins create accounts, under User Management.
Before turning it on: