Create new ad account in Business Manager
Steps to create a brand new ad account in Business Manager:
Go to Business Settings.
Click on the business account you want to use. If you want to create a new business account see this article.
Click Ad Accounts.
4. Click Add and then click Create a New Ad Account
5. Follow the steps to set up your new account and add a payment method for Facebook ad spend.
Finally, you can then enable this ad account in the dashboard here https://streettext.com/boost/facebook/ad-accounts/settings
Make sure to only click 'enable' on the ad account that you have created. Don't keep multiple ad accounts turn on at the same time.
Once you have enabled the ad account you created, click 'Manage' and start create some ads!