How can I replace a texture on the "Static Object"?

[Makiavel]

Yes, I loaded my custom model into the level editor, so there are two same models there now (since I failed to change the texture of the costume model). By loading I mean, that I pressed the "refresh" button under the entities list, and then saw the custom model in the sub-category (folder) I created.
But what exactly about renaming? Should I rename copied files in the explorer, or is it something else? I still don't understand.