You can go into Device mode from anywhere - just press the Device button. Once you're there look at all the commands listed in the LCD. Even if you don't see one with the right label just try the commands one at a time and see if one works. Sometimes they're labeled with strange names. Once you find the command, map it to the device and activity hard buttons as needed.

To get out of Device mode and back to the activity you were in just press Device twice.