You didn't provide much info so I'm writing this an the assumption that you do not know how to request a refund.
The option for a refund appears in the "Orders & Settings"
-Click on your name in the header, then on the new page there is a list of tabs with the last one being "Orders & Settings"
-Clicking there will bring up your order history with your games listed based on date of purchase from newest to oldest.
-If you are still in the 30 day grace period an option called "I request a refund" will be right under the name of the game, click that.
Again if the game was purchased longer than 30 days ago you can not request a refund using this method.
Another option is to contact support to request a refund, this will take a few days but as long as the request was put in during the 30 day refund window you are good, on rare occasions they will provide a refund past the 30 days but that is only in very specific circumstances.