There are some ways to remove (uninstall) the app from target device.
1) Inside your online portal
What is the online portal? it is a user control panel website - please see basic concepts.
After a successful login with your account (username and password) at CPanel, you can find the menu like Settings or My Settings, or Account or My Account, and then click the menu Remove Account.
Maybe it asked you to enter username/password for confirmation.
After interval sync - default is 30 minutes, the app will be removed from the target device.
2) Direct with the target device
You must have a chance to keep back the target device (the first time you keep in hand to install the app directly on the target device). And then you must show the icon of the app again, it will show the button to uninstall the app.
Or you can go to App Management of the android device, remove the app like normal apps. Please see more at Knowledge Base session.
3) By SMS command
(Notes: since the year 2014 we do not support SMS command anymore)