Michele,
It can be tricky to find the right folder as different versions/models/brands of Android Phones do it differently.
The easiest way is to upload your kml file as a Checksites event - This will give you a confidential 6-digit code that you can use to open the event on any device. (and you don't need to copy the file into a mysterious folder on your Android).
See:
http://maprunners.weebly.com/maprunf---checksites.htmlRegards
Peter