Harmonics can be difficult to learn, but keep trying. Once you get the knack of making them happen then they become pretty fun to add here and there in almost any song.
With no capo it is easiest to do harmonics on the 7 fret. If using a capo, find the fret that is nearest the center of the resulting string length. Lay a finger gently across all strings near, but not on top of, the fret. Then, as you strum, quickly raise the finger off of the strings, all at once. (Timing is everything) Take your time and practice until you can hear the ring come out. (Be patient with yourself.)
I hope this helps.