Step 1: Create a new currency in vBShop, points table user and points column dbtech_vbactivity_points
Step 2: Turn off points accumulation in vBShop for this currency
Step 3: Edit the items you would like to sell for vBActivity points and point them to this new currency
If you have not deleted the default vBCredits currency, you can follow the same steps except use credits for the points column.
You will then have 2 currencies that are gained in 2 different ways that can be used for different items.