Are you talking about a second either internal or external drive here?
If this is an extra drive that has been connected to the system if you told linuxmce to use it. It should have mounted that drive as accessible.
If not you can either change the permissions on the root mountpoint and do it recursively which will effect all files on the drive or you can change the owner to be linuxmce.
To change the ownership a command like the following would perform this for a drive mounted as /mnt/data
chown -R linuxmce.public /mnt/data
To change the file permissions to give everyone in the system read/write access would be somethin like
chmod -R 0777 /mnt/data