I need to edit a file within XTerminal but I do not know how to do this.

To explain a little more, my tablet is not showing the "Switch to Offline Mode" option in the power button menu. I had this problem once several months back and I just reflashed to fix it. I'm looking for other solutions this time and in another thread, namely this one, tell me to edit a file called "/var/lib/mce/mode" and put the word "normal" at the top of it. Sounds simple enough except I'm in the newbie forum here because I don't even know how to "edit".

Any help would be greatly appreciated.