- Open Firefox, type about:config in the address window, and click enter
- Right click on the window and choose New, then String from the pop-up menu that appears
- In the first pop-up box, enter: network.protocol-handler.app.mms
- In the next pop-up box enter the path to Vlc (e.g. /usr/bin/vlc)
- Now, click in the main window again but choose New Boolean
- In the first pop-up box, enter: network.protocol-handler.external.mms
- In the second pop-up select True