Custom Model Help

[Zack11]

Okay so i'm attempting to create some custom models for Amnesia with almost no modelling experience at all, in retrospect, not a good idea...

I discovered that the models are all .dae files and I know that these can be opened in Google Sketchup, so I did just that.

I opened one of the doorway models and alterted it slightly and then exported it as a .dae file again and attempted to import this into the Model Editor, The problem is the model is completely invisible... I've tried applying a material to it but it still remains invisible

The answer to this problem is probably incredibly obvious but as I said i'm a complete amatuer and blender confused the hell out of me, I'd be incredibly happy if I were able to make all my models in sketchup as I have plans for a mod in a more modern setting and only having my custom textures on planes isn't that great.