The Google AdWords Customer ID is a three-part number that is assigned to each AdWords account. For more information, please click here.
If you are a client account manager, you will need to enter the Customer ID of the client of interest when prompted to do so during the import process. You can find the Customer ID on the top-lefthand corner of your account underneath the client account name. Keep in mind that your Manager ID is different from the client's Customer ID.
For non-manager Google Adwords accounts, DataHero will automatically enter the Customer ID for you.