This is just a brief into/example. To really learn this, look for alternative resources. (See the “Links to Other Music Sites” in the sidebar).
The basic pattern for making a guitar sound harp-like is to alternate notes “chimed” at (usually) 12 frets higher than fretted with notes played in the normal fashion. Some guitarists use pick and 4th finger; some use thumb pick and fingers; some use just fingers. Each harmonic, though, requires at least 2 fingers of your picking hand to execute it.
As a starting point, play at the 12th fret, and do not make chord with your left hand (we will get to that). The openly played strings will be D, G, B, and E, low to high; the harmonics will be played on E (6th string), A, D, G, B. Then there is a role-reversal of sorts (this is just one way of doing it). You can see this in the following sketch in the 2nd bar.
Some of the great jazz practitioners of this technique that I am familiar with are Ted Greene, Martin Taylor, Lenny Breau, Phillip DeGruy, and many others. Most classical guitarists are use this technique as well, when appropriate. For example, a perfect use of this technique is used by Lagoya & Presti in their recording of Debussy’s Claire de Lune.
Lagoya & Ida Presti
Ted Greene, Martin Taylor, Lenny Breau, Alexandre Lagoya and Ida Presti