If you are working with an agency, for example, you might need to give access to your Google Tag Manager (GTM) account.
To add users to a Google Tag Manager account:
1. Click Admin.
2. In the Account column, select User Management.
3. Select Add new users.
4. Enter one or more email addresses.
5. Set Account Permissions. ...
6. Optional: Set Container Permissions for each container that you would like the user to have access to.
7. Click Invite.