On this page:

Select a shopping campaign from the campaign tree on the left. This will run the refresher on all active ad groups in the campaign and show results.

By default, the new product groups and ad groups created will inherit the bids from their respective level at the Everything Else node. You can choose to overwrite the bids using the "Set Bids for Selected".

To do so, review the product groups to be added (Additions), select the ones you want to change bids for, and press "Set Bids for Selected". This specifies that only the new additions will get these new bids. 

Once you click apply, you will have the option receive an email once optimization is applied. This way, you won't have to wait for the process to finish loading. You'll be notified if there were any errors, and/or if the changes were applied successfully.

The Shopping Refresher can be automated to run on a schedule, allowing you to re-sync your feed automatically. 

You can find the details of past and scheduled automations in the Automation Schedules and Automation History pages.