1 500s is only for sat.
2. you need the software all available on the net. you will need:-
1. dreamup
2. dreamedit
3. flash wizard
4. image of your choice
hardware
1. null modem cable.
2. cross over network cable.
I am not being rude or anything here, but woudnt it have been a wise move to read about the process before purchasing the dm 500s so when it came you were educated on what to do and how to do it with all necessary files/cables required (anyway thats how I work)
but to answer your question you can flash it using 2 methods
using Dreamup - required null modem cable - best method I find
ftping image to box and flashing it via telnet - box needs connected to your network, not as easy as dreamup as it requires more steps