Outside of the Model Editor (which is used to create entities), your exported Blender model would be considered a static object. To make use of it simply place down a static object in your map and then replace it with your own model. Do note, though, that each texture of your model requires their own material file (which you create using the Material Editor). If you want to make an entity out of your model, simply open up the Model Editor and go to File > Import Mesh, and select the .dae file for your model, then save the entity.
Read up on the wiki Blender article if you run into any issues importing your model into Amnesia:
http://wiki.frictionalgames.com/hpl2/thi...3d/blender