To change permissions on a file, you would use the "chmod" command type "man chmod" at the console to learn more.
But basic syntax is like this "chmod ??? /file"
Where ??? is the permissions you want to assign it can be a combination of rwx,
The first ? is for you the owner of the file
The second ? is for the group that owns that file
The third ? is for everyone else
you would be better off learn about the number system ie 777
also look into sticky bits and guid etc.
To change permissions on mounting issues look at the /etc/fstab file.
It has the permissions in there for mounted filesystems once again you can "man fstab" to learn more.