to test the backup -which is done by third party software
How you restore really depends on how you backup the database !
Without knowing how the backup is done it would be incorrect to advice a single method to test restoration.
Nevertheless, you need to start with an installation of Oracle software (RDBMS, Binaries) on the new test server. You would have to install the same Oracle RDBMS Release and Version as the one that is running in your production server (where the backup was taken). If the third party software incorporates media management libraries, you'd need to install and configure them as well. Thereafter, the restore command depends on how the backup is done.
The third party software is just an interface (this is what I'm told),it does a full DB backup using RMAN in the background...
What I have to do (to confirm the software credibility) is to test this full backup on another server.