this is not right forum, but not yet find solution and I hope that maybe some has published unreal game in steam. Next problem when try to run_app_build dir etc I always get error :" error empty depot section " I have that depot, and for my opininon making simple games is easy, but publishing in steam for newbie is very difficult 
You’re best off reading the Steam documentation on uploading builds, failing that posting here: Steam Community :: Group :: Steamworks Development