After subscribing if you still see ads in the app you are sharing the subscripiton with, try force quitting and reopening that app.
If you want to manage your subscription simpily open your profile settings in any app, by going to the profile tab, then tapping on the profile image.
If you are in the app that is sharing the subscription, you should see an option to manage the subscriptoin in the other app, tapping this row will open the main app, and load your profile settings where you can see and manage your subscription.