Many agencies and consultants (us included) use MCC AdWords accounts for multiple client account access. In this case, give your customer ID number from your AdWords account to your AdWords consultant:
They will then request client approval and you’ll receive an email from Google for you to accept the request. However if you miss the email for whatever reason (spam, too busy, all of the above) then you can accept it via your Google AdWords account by accessing your account settings >> account access >> accept client manager request. Dead easy – but here are those steps in screenshots:
