Through the connector menu or the contextual bar, navigate to the ad accounts. The homepage will be an empty list, with a button above the contextual bar that allows you to add a new ad account.
To configure a new ad account, select it from the dropdown menu and optionally enable real-time synchronization.
Once you have selected the ad account, use the Add button to complete the configuration. The result is shown in the image below:
This screen displays the information needed to identify the ad account and to view or modify the status of real-time synchronization (if you have the required permissions).