when you type "/etc/tor/torrc" it says premission denied because you are trying to execute the torrrc file. you have to type
than press "a" key to start editting the file. You can than save it by pressing Esc, and write :wq (which will save the changes to the original file and exit the vi)

If you are unfamiliar with vi editor, you can install nano (much easier, I am using it too)

However, if you want to edit the file in your home direcotry with some GUI text editor, you can. You can copy ti back by executing (same like previous command, but backward. Makes sense isn't it?)