Each group of 7th chords are based on a I vi IV V progression in the keys of C, G, D, A, E, B and F.
Before attempting to play with an exercise, start the exercise to see which chords will be used.
First, try to familiarize your fretboard hand with the chord shapes.
If you have difficulty playing a particular chord, do your best to place your fingers on the correct numbered positions; 1 = index finger, 2 = middle finger, 3 = ring finger, 4 = pinky.
If the chord does not sound clear at first, do not worry. Over time, you will develop the hand strength to make the chord sound better.
After you hear the 4 beat count-off, attempt to strum each chord in tempo with the exercise.
Use your guitar to play along with each chord exercise.