Once you have added a user to your organization in Proton Mail(new window), you can assign them administrator privileges. To do this, sign in to account.proton.me(new window) and go to Organization → Users.
Next, in the Action column, click the arrow pointing down next to the user you wish to promote to admin status and select Make admin from the dropdown menu.
On mail.proton.me(new window), you can do this by navigating to Settings → Addresses/Users → More → Make admin.
Once the user is assigned as an admin, they will need to log in into their account and activate their admin status by entering the Organization password(new window) that you chose when you created the organization.
If the user is already an admin, you will see the option Revoke admin in the same dropdown menu.