Whether it's a coworker, an employee, your client or your PPC manager, you can grant access to your account through your dashboard.
Sharing an account will give another user access to your domain with their own set of login credentials.
On the top right corner of your dashboard's screen, click on Account > Share Account:
Click on Share Account with New User.
Fill out the email address to which you wish to grant access and then click on Send Invitation: