Those are only examples of two power chords on the low E string. Keep moving up fret by fret and there you go. You can also do the same stuff on the A string with the same three finger pattern. But once you get to the D string, things get complicated. Check out this helpful chart below.
E Power Chord F Power Chord x| x| x| x| x| x| d|2 d|3 a|2 a|3 e|0 e|1