AdWords: Accept AdWords invitation and grand MCC access
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.