If you want to create a brand new model from scrach, Icedesign can be used to create the Item Definition and a directory for you to place the files (named correctly).
Your file explorer will now be opened in the correct directory. You will place the OGRE .xml mesh files in here, as well as any textures. You can also store any native files your 3D editor might use (such as .blend files). If you do so they may be opened from within Icedesign.
To get any idea of how the filess in this directory should be named, consider cloning an existing item for an example.
Use the following if you want to copy an existing item, and alter either its textures or mesh.
Your file explorer will now be opened in the correct directory. You will see the OGRE .xml mesh and texture files in here. To view and edit the textures, see the section on Editing Items.
Any items that you have stored locally in your workspace may be Edited. This allows editing of textures (by launching your systems default image editor), editing of .blend files (when they exist), editing of colour maps and more.
A window will popup listing all of the resources used by that item.