It may depend on which SLAMM version you are using. However, in general you click edit cells, make your edits using draw/fill cells, and when done you may simply close the window and you will be asked if you want to overwrite the raster (the raster will have same name as the original one but with the edits) or click "Save As ..." and save the raster and project with different names. Hope this solves your problems.