I also can't remember how to do it, but I would do it by first looking
in Word's Help. You can search for "footnotes" and you'll should easily
find the article "Restart footnote or endnote numbers".
In order to restart footnote or endnote numbering you first have to be
familiar with the use of Section Breaks. By properly applying them you can
restart the note numbering on a per section basis. Look them up first.