this even easier than you think
the root note is the note that in the name of the chord:
for example E's root will be the note E
now simple major or minor chords are build from three notes
and the quality of the chord depends on the third note.
the 2 basic form of chords are:
the root note, 2 tones, which are 4 frets on the guitar from the root, and a 1.5 tones which are 3 frets from the second one, and usualy this note will be the fifth note from the root (in e it would be b). this chord is a major one
to change it to a minor one you should lower the interval between the 2 first notes to a 1.5 tones, and then the second interval will be 2 notes.