You will be directed to the rewards store homepage. Click on Purchase from the menu on the left hand side of the page.
You can then select the student you wish to make a purchase for from the dropdown menu.
Once you have selected your student you will see their points balance on the right hand side of the page. You will see a list of available awards with their price and if the student has enough points, you can click the Purchase button to initiate the purchase on behalf of the student. Please do remember that the order will not be automatically set as fulfilled in the Orders tab.