Actually, the easiest way is to install hijack onto the player. Then go into your browser and type the following:
http://empeg.address?rw
Done.
Of course then you're still going to want some type of interface to put stuff on the player. So even though that's the EASIEST, you'll want to use an FTP client to do uploads and downloads. With FTP you can also use SITE commands to mount: SITE rw and SITE ro. As well as SITE reboot.
Read about all this stuff, and more, in the PROGRAMMING forum. This all assumes you have an Mk2 or Mk2a and the empeg is connected via ethernet.
Bruno