Summarize the following:
" Log into your Steam account. Click on the "Steam Help" tab near the top of the screen. When you click on "Steam Help," you will be redirected to a list of options. Near the bottom of the list, you should see the option "A Purchase." Click on this. After you click "A Purchase," you should be directed to a list of games you purchased on Steam. Select the game you're looking to refund. You will then be presented with options to specify the problem with your purchase. Select the reason you're refunding the game. Options include things like "Gameplay or technical issue" or "I purchased this by accident." On the next screen, select the option "I'd like the request a refund." You can then fill out a few notes explaining the specifics and hit the "submit" button. For example, in the notes field, write something like, "I meant to purchase the newer version of this game and it wasn't clearly labeled on the site."

Summary:
Go to "Steam Help. Specify you need help with a purchase. Select the game you want to refund. Explain the problem. Request a refund.