Plug the HDS into a TV and get a picture from it displayed.
With the remote control, select Main Menu.
Scroll to Settings. Enter.
Scroll to Slingloaded. Enter.
Message will appear asking for password. The default is 0000 so type this in.
Then you should see..
Top item (at least on my HDS) is Slingbox ID.
Press right arrow to highlight Slingbox ID and then press enter.
Now should be displayed the long combination of numbers and letters, which is the ID
That is what happens on my HDS. Only problem maybe if the default password was changed.
Write down the ID and then back out of the menus using back key.
Hope this helps.