I'm using ettercap. I have instructions to change the content of the file: etter.conf. I can't change the file since it's read only, I also can't change its permissions since I am not the owner of the file.
Is there a way I can edit the file's content?
You can not edit a file, if you don't have the required permissions.
However, you can use sudo, if you need root access to edit file.
If that does not work, then you can use other way, prescribed by software vendors.
Just use cp etter.conf etter-new.conf, to copy the file and then use the new one.
Don't forget to backup the old one.