A feed is a file that contains a list of products you want to advertise through Merchant Center. When you add your products, you'll assign attributes to each one. Your product feeds will use these attributes to group your products together.

Sign in to your Merchant Center account. Select Products from the navigation menu, then click Feeds. Click the name of the feed you'd like to schedule. Click Settings on the subpage menu on the left, and select the type of schedule from the drop-down menu beside Fetch schedule.