By default a list of Sources are made available to your account. Sources are nothing but publisher sites & search engines on our network. Upon assessing the performance of Sources that you are using based on the Impressions, Clicks and CTR they generate; you can add the Sources that work best for your Campaigns to Favourites. You can simply add your Favourite Sources for any new Campaigns you set up – instead of having to recall them.
To use Favourite Sources when adding Sources, select ‘View Favorites’ from the ‘Filter by’ drop down list seen on the Add Sources page.