I'm from Poland and I apologize for eventual errors in this text.
Maybe I'm stupid but:
How can I open downloaded map in Fear and Loathing, and how can I play it?
to play it you just put the map (unzipped/unrarred/.../whatever) in the plugins folder in your myth-map
to open it in fear or loathing you first have to extract the map with a tag-extractor, put those files in your local folder and then you can see them in fear/loathing