Each social media site has a management section for 3rd party access given by the account owner. To revoke the permission to any application, the connection is managed from social media site.
When on the mobile app, click on the account you'd like to make the change to. Then select the 3 dots option near the top right and the option to 'Open Account' will appear and take the user to that profile. Each social media profile will be different as far as where that management section is.