su
mount -o remount,rw /systemmount -o remount,rw -t ext4 /dev/loop0 /
For Bliss 11:
Use the alt-f1/f7 console, then enter:mount -o remount,rw -t ext4 /dev/loop0 /system
After that is done, you can edit the system files you need. When you are done, you can close the terminal app or use alt-f7 to get back to Android if you are using the Console.