There are several ways to upload your interface to your mrmr client. If you use a Macintosh, the easiest way is by pushing the new interface by using either the Interface Builder application, or by using the demo server application.
However, you may also simply upload your text file (it is customary to give mrmr interface files a .mmr extension) to a webserver and retrieve it within the Mrmr client itself. Look for the ‘Download from URL’ option in the Open dialog in Mrmr.
Once you have your new interface on your device, don’t forget to ‘Save’ it so that it will be there the next time you use Mrmr!