Peer to Peer giving is the place where you can control how much money each user has to give each month. But keep in mind they are able to use their spending money to give as well.
If you want to give your users a reward for using all of their giving money, The Sweetener is where to go. By doing this they will receive extra money in their spending at the beginning of the month.
If you need to give your users more giving money, but you only want to give them extra money once. Click on the arrow next to your name in the right corner. Click on 'Admin Tools.' Once there click on 'Manage Cash Giving' underneath the tab 'Appreciations.'