(– by moejeep #5369 –)
The file your are trying copy is compressed (.ZIP). Before you copy it you need to un-compress it (or unzip) it…
On windows you would right click and select "Extract Here" or "Extract All…" but by the screenshot it looks like you are using a mac/apple.
Here is an example of you can do on windows:
Lets say I downloaded: trailindex-gps-ShoeLake.zip
If I right click and select extract here, I will now have another file: ShoeLake.gpx
I could then click on that file, drag and drop into phone GPX folder.
Also in windows there is an option to see the file extensions, most users have that off, therefore you might not see zip or gpx if Mac/Apple is the same way. In the description of the file is says 'Compressed File' it should say 'GPX file' when it extracted.
Anyone reading this know mac/apple?