Kyle,
I no longer have Finale 2009 installed on my computer. However, once you've added the additional staff you will need to assign the percussion map from within the Staff Tool > Edit Staff Attributes. Set the notation style to Percussion and using the button next to this option, select the VD: percussion map for the instrument assigned to that staff.
As mentioned above, I no longer use Finale 2009 but you may need to select the percussion map from within the Instrument List as well. I'd suggest consulting the Finale Help as well as relying on my bad memory.
Let me know if there are any more questions.