Meta Ads works with one or more accounts at the same time. At the top of the page, click the account selector button, use the Search accounts field to find accounts by name or ID, select the ones you want and click Open. The Clear button deselects everything so you can start over. With more than one account open, the table and the Period Summary combine the data from all of them. Next to the selector there's also a Privacy button, which hides the account name on screen, and an external link button that opens the selected accounts directly in Meta Ads Manager. If the list takes a few seconds to load the first time, that's normal: Meta can take a while to return the accounts for users with access to many.

The selector has Select all (selects the accounts in the list, respecting your search), Shift + click to select a range, and the account groups from Account Center in the Groups (N) row, with Save as group to save your selection.