Hi.
Itch is a game store with more than half a million games. Getting help for a particular game in this section is very complicated, the best thing is to ask the question in the comments part of the same place where you downloaded the map.
Regarding your question, as far as I know, the itch application cannot patch another game, that is, the application does not know what to do with a map, even though the game that uses it is also available on itch.
You should manually download the map and apply it in-game, unless it's an installable, in which case, it's also out of Itch's application scope and you'd have to check with the person who created the installable.