Like said above your going to need a existing game that allows you to import your own models. Such as Unreal Tournament. Which comes with Unreal Ed. So you can make your own maps and import your own models.

If you don't have unreal, you could try searching for a free game engine online. I'm sure you can find something.
Though you may need to do some programing to get things set up.

Other than that. If you want to see your content in game without the hassle of Finding/ making your own game, perhaps you could join some form of Mod?