setting up and linking adwords accounts to Google merchants accounts

 From: https://support.google.com/merchants/answer/2660968?hl=en 

AdWords settings and account linking

You will need an AdWords account that is linked to your Merchant Center account in order to set up your Product Listing Ads campaign. This allows your Product Listing Ads campaign to use the product data you submit in your Merchant Center account. You can either:

A. Create a new AdWords account;
B. Use your existing AdWords account to which you have Standard or Administrative access;
C. Use other AdWords accounts linked to your Merchant Center account;
D. Link another AdWords account to your Merchant Center account.
Learn more about AdWords account access.

These four options for linking your AdWords account from Merchant Center are available under “Option 1” and “Option 2” on the AdWords tab under “Settings” in your Merchant Center account.

Option 1

A. Create a new AdWords account

If you don’t have an AdWords account, you will see a blue “Get Started” button under “Option 1” on the AdWords tab in Merchant Center. Click on this button to start the process of creating your your AdWords account and Product Listing Ads. The next two articles in our Getting Started Guide provide more details on this process.

B. Use an existing AdWords account to which you have Standard or Administrative access

If you already have Standard or Administrative access to an AdWords account that is listed under the same login ID as your Merchant Center account, you can use this AdWords account to set up your Product Listing Ads campaign. Click on the blue “Set Up Product Listing Ads Campaign” button to start the process. The next two articles in our Getting Started Guide provide more details on this process.

Note: You will need at least Standard or Administrative access to the AdWords account you would like to use to create a Product Listing Ads campaign from within Merchant Center. If you have accepted an invitation for these access levels to an AdWords account but your access has not been granted yet, please contact your AdWords account administrator. Learn more about AdWords account access.

Option 2

If you have Email-only or Read-only access to an AdWords account, or would like to use other AdWords accounts to which you do not have access, you can choose from the following linking options:

C. AdWords account linked to this Merchant Center account

There may be one or more AdWords accounts owned by other users (e.g. colleagues from your organization) that are linked from your Merchant Center account. Even though you don’t have Standard access to those AdWords accounts, you can do the following:

Choose the specific account from the list that you would like to use for your Product Listing Ads campaign, and contact the owner of that account.
The owner of that account can either give you access or can log into Merchant Center themselves and set up a Product Listing Ads campaign using that AdWords account.
You can also change the linking status of one of these AdWords accounts by selecting one of the following:

“Activate” will allow a linked AdWords account to access your Merchant Center account;
“Deactivate” will disable the link between that AdWords account and your Merchant Center account;
“Remove” will permanently remove the link between an AdWords account and your Merchant Center account.
D. Link another AdWords account

If there is an AdWords account that you would like to link to your Merchant Center account to create your Product Listing Ads campaign (e.g. for an Ad agency that may be managing your Ad campaigns), you can enter the AdWords Customer ID for that account and click “Link Account.” The owner of that linked AdWords account can then sign in to AdWords and set up campaigns on your behalf directly in AdWords.