When you import a map from Maps4Cim the thumbnail for that file normally displays for the map shoes the name in green text.
Open the map in the editor, checked that it OK, then save it under your required name (you must type this in the empty box). The green text will be replaced by a thumbnail of the map (in the list of files available for editing).
If the green text is still displayed after you have saved and closed you map, it will indicate that your save has failed.