To remove your the Facebook account you added to the Oasis software you will need to log into your Facebook Account and go to the "Settings" of your personal profile.
Scroll down and click "Business Integrations"
Now look for the integration labeled "The Oasis".
Click the checkbox and then click the remove button.
You have successfully removed the Oasis App from your Facebook Account.
You can add another account by following the article on Connecting Your Facebook account to the Oasis App.