You need to pay $100 to upload it to the steam green light. Then People have to vote for it to be added to steam. Then you have to wait around 2-3 weeks to hear from steam to add it to the Steam Market.
Buildbox is the world's first software that truly allows anyone to create amazing games regardless of technical skill. Due to it's unique user interface, making games becomes a fluid process that doesn't require any scripting, programming or software design experience.