Uninstalling Fomo on your BigCommerce store is easy.
First inside the BigCommerce dashboard you have to navigate to 'My Apps'
Once you are in 'My Apps' to the side there is a panel list of all of your apps and each one has a launch button on it. To the left of the launch button there is a small uninstall link. You can click the uninstall link on the Fomo panel and that will successfully remove Fomo from your shop and cancel all billing unless you already have a pending charge.