You can share your AdWords account with a person or a marketing agency.

Grand AdWords MCC access to another party

Click on the gear-icon in the top menu on the right and click on account settings.

Click on account access in the left menu. You see a list of users which have access to your AdWords account.

Scroll down to Client Managers. Find the e-mail address you expect an invitation from and click accept request.

Your account is shared.