You would first perform a hard reset on the slingbox unit (Hold down that little button on the back for 30 seconds)
Then you hookup the slingbox to the network you want in to run on.
Then on a computer on the network go to http://setup.slingbox.com and run through that
This is important:!
Make sure internet viewing is complete or your slingbox won't be able to stream over the internet. The message it has to say is "Internet viewing is ready." If you get a message other than that you need to portforward the slingbox on port 5001 or whatever port it wants based on the advanced settings.
If you don't know how to portforward your router the best way to find out is to google "'Router make & Model' Porforwarding guide"
Hopefully this helps