So I pretty much copied out a whole tutorial on making a realistic scene. Then I realized I done it all in blender render and cycles render, is there a way I can make it capable of being game engine? Thank you
I guess a lot of the things you already did will work with the BGE.
You might need to tweak materials and settings here and there to get the desired result.
Be aware not all modelling options are available. E.g. particles and curves are not supported by the BGE.
The animation systems are different (Blender is timeline driven while the BGE is event driven). So you will need to add the BGE behavior on that (you can use the actions of the Blender animation).
The Physics systems are different and require a complete different setup.
The Renderers are different (realtime renderer vs. non-realtime renderer) and not compatible, but can result in similar results. Due to the different requirements the BGE renderer will support less features than the Blender renderers. You can bake the output of the Blender renderer into materials and textures which can be presented by the BGE realtime renderer. Be aware not all details can be baked (e.g. reflections).