Duplicating an existing app gives you the possibility either to create a back-up application or create an identical application for a different platform.
Below you may find some quick instructions upon how to duplicate your existing application.
1) Access your account at App Builder
2) Go to your app's dashboard
3) Click the "Duplicate" link.
4) In the pop-up window select the target (depending on the purposes of duplicating the current application), type in the new app name.