Help needed with playing different towns in The Sims 3

[MusicalSim]

I have downloaded the new town Riverview but cannot seem to find how to get away from Sunset Valley from the main menu screen and enter Riverview. I tried the option of starting a new game and appear to have deleted the first game I started in Sunset valley. The instruction booklet that came with the Sims 3 does not appear to cover this. Please can somebody help tell me what I am doing wrong, it would be very much appreciated. Thank you. :help:

[JackFlash]

Once I installed the Riverview town, from the main menu, when I clicked on the Start New game, it gave me the option in a drop down of playing in Sunset Valley or Riverview?

[MusicalSim]

Thank you JackFlash for your prompt reply. I had Riverview installed when I first tried out the "start new game" option but lost my original Sunset Valley game. I have now tried again as you suggested, after saving my game files, and it works just fine. Must have been a problem somewhere but the game is playing fine in both towns. Cheers