There is nothing that can be fixed here, because automatic downloads can only be provided for official maps. We just need to explain more.
ProTux {l Wrote}:where would "save file" appear? when i clicked on the downloads thing all it says is download complete and "show in folder". what do i do? i have windows 10.
Select "Show in Folder".
For finding the supertux2/addons/ folder:
In File Explorer, click into the field on top where you see "This PC -> Downloads" or something like that. It will become blue, so you can type a name of a folder to replace what's there. Type the following:
%appdata%
and hit the "Enter" key.
This will take you to your personal "AppData/Roaming" folder.
You should find a "SuperTux" folder there, which in turn contains "supertux2/addons"