From the Admin Dashboard, follow THESE instructions to add a new guardian to a student's account. If you'd like the guardian to be able to use the Switch Accounts feature, be sure to enter the exact same email for the guardian on both students.

If you choose to send the sign up link immediately, the guardian will be emailed and asked to link to their existing account once they click the "Create Account" button in the email:

If you copy the email and send it to the guardian manually, they will be asked to create an account as they initially did and Playground will link the accounts on the backend so the guardian can use the Switch Accounts feature.