Editing or Adding Grub 2 Menu Entries

Open these three entering via terminal 

$ sudo gedit /etc/default/grub

$ sudo gedit /etc/grub.d/40_custom

$ sudo gedit /boot/grub.cfg

From the grub.conf copy the content which starts from 
#BEGIN
menuentry

After u done that you run the command :

$  sudo update-grub