Where can I find functions.php?

I asked this a while ago without a clear resolution so here it is again:
I need to post a snippet of code in my functions.php file for a plugin but I don’t know where to find it. I googled it and in every instance the suggestion is to go Dashboard-Appearance-Editor. Thing is I don’t see the editor option under my appearance menu. I don’t have access to any of the hosting details so I can’t use FileZilla or anything. Is there another way to access functions.php through the dashboard or without the need to access the root directory.