The beginning and the theme both start on middle C. So, for instance, when you play the part that goes "when I see your face", you play C C F G A and the beginning would be alternating using third finger C and first finger A on the G string. Then you can just go off from there if you know how it sounds (that's what I usually do). Use your musical sense to guide you. I don't have the music notes so this is all I know since I learn pop songs by ear.
By the way, this version of it is in F Major meaning B flats!
