If you are referring to the Alpha Keys, they should be sent out at the end of the day that you purchased it from Indiegogo. If you haven't check your Spam Box, or send an email to Contact@pixeltailgames.com with "Serial Key Please" and include the backer e-mail address.
If you are referring to Steam Keys, the game is not yet out on Steam, and the keys will be mailed out when it is.
Also Remember, Steam Alpha and Early Access are different. Early Access Keys will be shipped March / April 2016.