Account Groups are great way to group similar ad accounts (cross-network) and have all of their data in one place. When coupled with the visibility toggle, you are able to display or hide all of the ad accounts that pertain to a certain client, or demographic (ex: domestic vs. international).
Step 1: Navigate to the Accounts page of your account by hovering over The Data Management icon on left-hand sidebar.
Step 2: Use the selector boxes on the left-hand side of the page to select the accounts you'd like to group together
Step 3: Once you start selecting accounts, a toolbar will appear at the top of the page. Click "Create New Group", then name your new account group.