For general instructions on how to connect your Facebook ad accounts, please refer to this article.
Yes, you can connect as many ad accounts as you need as long as they comply with the ads policies. Just toggle them on in Integrations and wait for a bit till the review is finished.
If there are several personal Facebook profiles connected to Bïrch and these profiles have admin access to the same ad account you can change the main profile the particular ad account works through.
IMPORTANT: If some of the ad accounts are connected to Bïrch via the profile that you would like to unlink, please make sure you re-select another profile for these ad accounts before removing the old profile to prevent the rules and reports from turning into drafts.
If you have hundreds (or thousands) of ad accounts associated with connected profiles, you may not see the full list under Facebook Ad accounts. In this case, please use the search function and enter the name of the ad account to find and connect it: