Google Remarketing Tag is used to reach out to customers who have browsed your online store. After tagging a page on your online store, a remarketing list of customers who have visited the page is generated. Merchants can then build remarketing campaigns targeted for this remarketing list of customers when they search on Google.
Sign in to your Adwords account and go into "Shared Library".
Click on the "Audiences".
Click on "Set up remarketing".
On the pop-up page, click on "View Adwords tag for websites".
Copy the Google Conversion ID as shown in the picture.
Go into your Admin Panel, then add a Google Remarketing Tag in "Tracker Settings".
Pick an action to track and paste the Google Conversion ID.
Don't forget to click "Add" to save your tracker!
You should be able to see the following sign on the upper right hand corner of your Audience page if you successfully added the remarketing tag.