After you "brouse" and select the Rx file there should be 2 items in the box on the Viper screen. 1 item for "rate" or "amount" and 1 item for "name" or "ID". You select the rate or amount. This will put a red box around it. Then continue to start the job. Your Rx tab should be availible and you should see all of the rate change squares.

Remember the Viper operates on pounds per acre so if you are doing lime check to see if the map was created in pounds or tons. If it was created in tons then you will need to enter a 2000:1 conversion factor while setting up the job.