The A-flat minor seventh (Abm7) chord is a four-note chord formed from the notes, from lowest to highest: Ab, B, Eb and Gb. Minor seventh chords are minor triads with a minor seventh above the root added to the chord. The added minor seventh gives the chord a dark, jazzy sound.c 

Abm7 chords sound complicated but aren't much more difficult to play than a simple Ab minor triad. To play an Abm7 chord, start by playing Ab minor triad. an Place your right thumb on Ab. Now, place your middle finger on B. Finally, place your little finger on Eb. In order to turn your Ab triad into an Abm7 chord, cross your left index finger over your right hand and place it on Gb. Play all four notes at the same time while keeping the volume consistent. 

With practice you can also play an Abm7 chord with one hand. To play an Abm7 chord with your right hand, place your right thumb on Ab, your index finger on B, your middle finger on Eb and your little finger on Gb. This might take some practice so try your best not to get frustrated. In time you'll get it down.