If you are an admin and you have installed the Virtual Currency app on your community, you can easily do the reward transactions to your member's accounts. You can "Deposit credit" to a user's account as a reward for their outstanding activity, or "Withdraw credit" from a user's account once the points are cashed out. 
To do these transactions, go to the user's profile account by click on the user's profile picture> click on the (...) button next to the "edit profile"> you can see the options to Deposit credit and Withdraw credit