To close your Sling Money account, tap on your avatar in the top-left of the 'Home' screen, scroll down to 'More', and follow the instructions to close your account.
Before closing your account, consider:
Changing your privacy settings
Unsubscribing from Sling Money emails (tap the Unsubscribe button at the bottom of any Sling Money email)
Uninstalling the app (You can reinstall and sign back in at any time)