Do you I need to sign a legal contract with Epic Games before commercializing my game product?

Hi, my name is Eric and recently I have created a Kickstarter in order to help fund my game creation project. The Kickstarter has not launched yet as I am still unsure whether or not I need a legal contract of any kind with Epic Games before I commercialize my product which was created in Unreal Engine 4.

Thank you very much.

Best Regards,
Eric