Set your metronome to a slow tempo. 60 BPM (beats per minute) is a good speed for beginners. Make the fist strike of your triplet match the click of the metronome; you can also count out loud, accentuating the first note so it sounds like, "ONE and a..."
Start with a basic sticking technique. On the snare drum, play all three notes of the triplet with one hand and then alternate. For example, play the first triplet with your left stick (LLL), and then switch to your right (RRR). Alternate back and forth repeatedly for a few minutes paying close attention to the metronome; do not speed up or slow down. Stay on tempo.
Switch the sticking technique. Play your triplet with a LRL, LRL, LRL stick pattern.
Build stick control by alternating your sticking so you play your triplet, RRL, LRR, RRL, LRR.
Play a triplet on a drum set. Split up your triplet so you play each note on a different drum. On the first count of the triplet, hit the snare drum. On the second count of the triplet, hit a tom drum. On the third count of the triplet, play the bass drum. Play snare, tom and bass repeatedly while building up speed to create the great Bonham sound.