The minor pentatonic is the most-used scale in blues and rock. It has five notes: the root, minor third, fourth, fifth and flat seventh. In A minor that's A C D E G.
Box 1 is the shape everyone learns first. It starts on the 5th fret, with two notes on every string, and the roots (A) on the 5th fret of the low E, the 7th fret of the D string and the 5th fret of the high e.
Fingering and picking
Put your index finger on fret 5 for every string. Use your ring finger for fret 7 and your pinky for fret 8. Your hand never moves: it's a box.
Alternate pick. The triplets put three notes in each beat, so every two beats cover three strings.
It should sound bluesy and open, with no "wrong" notes. That's why it's so popular for improvising.
The common mistake is flattening the index finger across the strings so notes bleed together. Use your fingertips and lift each finger as you move to the next string.
When the box is even, play the short phrase. It ends on the root on the 7th fret of the D string: add a little vibrato there, and try making up your own two-bar phrases that end on an A. The four-bar phrase comes home to the low A, and the last exercise moves the whole box up to the 12th fret for E minor.