If your Slingbox has been successfully set up- from any computer- you shouldn't need to set it up again unless there are configuration changes to be made.
In short: once the Slingbox is set up, any computer that can run SlingPlayer can watch it. All you would need is the SlingID if you're remote viewing, and nothing if you are on the same network (SlingPlayer autodetects Slingboxes over the LAN).
I prefer using the full Mac SlingPlayer program. If you don't have a copy, you can grab one here and try it.
If you prefer the Web Player, go to watch.slingbox.com and log in. You may need to update the Web Player plugin. If so, the page will walk you through that automatically. Afterwards, you should see your Slingbox on the Directory screen- click to watch.
Autodetected Sling Classic on the LAN.
Note the yellow dot- Sling Classic is too old for the Web Player. Your Solo will work though.
Slingboxes on the LAN are detected automatically, as shown above. If you're remote viewing and don't see your Slingbox, click Connect to a different Slingbox and enter the SlingID. You can also go to accounts.slingbox.com and add it there.
If you don't have your SlingID, here's a support doc that tells you how to find it:
Hope this helps ! Post back if you're still having problems. More details about what is happening and how you're connecting would help.