A pre-requisite for this app is that your PVR is connected to your home network.
For this app to work you will first need to download and install the TMSRemote TAP onto the Topfield box and set up its port and password.
(Download the TMSRemote TAP from here: http://www.topfield.cc/files/Firebird/TMSRemote.zip)
Once TMSRemote is setup and running, run the iTMSRemote app and select the Settings button and enter your PVR's address, and the TMSRemote port (1413 by default), and password (if any). Then select the Play button.