You don't say what you are trying to view, ie sat, transponder? And you don't say what Dish Network system you have.
You say you are using a Dish Network dish? If so, I hope you realize that you will only be able to receive FTA signals, not the scrambled ones. That limits you to basically the music channels and two or three other channels, such as NASA-TV. Also, if you are still using the Dish Network receiver to control the dish switching, you will be limited to whatever satellite and polarity the Dish system is using at the time.
Unless you have one of those Dish "Super Dish" things, that have capability to view linear sats, the circular Dish Network LNBs are only compatable with the DBS satellite, which limits you to the Dish Echo sats and the Canadian Nimiq sats, but most of the signals on those sats are scrambled. Also, even if you switch to a linear LNB, the regular Dish network dish is too small to receive the conventional satellites.
However, if you want to experiment, and try to receive music and NASA-TV, with the circular LNBs, you'd want to set the LO freq in VisionDTV to 11250. All the scrambled channels will come up unable to play, but if you look up the info in Lyngsat (
http://www.lyngsat.com/echo7.shtml ) for the few free channels there, you should be able to play a few signals there.
If you have one of the "Super Dish" things, you may be able to watch some FTA signals on other satellites, if you re-aim the dish, however then you wouldn't be able to use your Dish Network dish for it's intended purpose.
Anyway, just what are you trying to watch.