If you need to add some html for tracking or a widget that goes on every page you can edit this in either the header (top) or footer (bottom) of page
For tracking code you can use the header if in doubt (put they often will say at top or bottom when saying where to add code! (header =top; footer= bottom ;)
So login if you aren't already click on web editor and click the pencil by the header code or footer code
So go to your file (if its a file) and open it and copy the code or if its just code to copy then copy that code!
And paste it in your header or footer code editor and click save!
That's it! You're done!!!