The following steps will walk you through giving access directly from your Google Ad account:
1.Log into the Google Ads account you want to grant access to.
2. Go to Tools and Settings in the top right corner.
3. Choose Access and Security.
4. Hit the blue + button
5. Add the email address of the person whose account you want to grant access.
6. Select the permissions you want to give them.
7. Click SEND INVITATION
8. They will be notified through email when they have gained access to the account.