Just a heads up if anyone stumbles upon this old thread.
The jmonkeyplatform, .jmonkeyplatform and .jmonkeyplatform-installer folders are at /home/<user_name>/ . This is the default target of the jME installer.
And among these three folders, two of them, .jmonkeyplatform and .jmonkeyplatform-installer, are hidden by default. To see them in the file manager(nautilus in ubuntu) you’ll have to press Ctrl + h(unhide hidden files).
And if any of the chmod command results in following error,
chmod: changing permissions of ‘.jmonkeyplatform/3.0/xyz’: Operation not permitted
Try using sudo. For example chmod -R 777 .jmonkeyplatform would be sudo chmod -R 777 .jmonkeyplatform
I am using Ubuntu 14.04.