The pulse is a regular division of the time space. In a piece of music, the pulse is not always played by an instrument. It's beat can be implicit, felt as an integral part of the rhythm.
The rhythmic question is often overlooked. However, it is the foundation of music and a key to playing with other musicians. This exercise aims to train you to place a percussion rhythm within a time space defined by the pulse.
Listen attentively to the introduction of each exercise and try to internalize the pulse outlined by the voice: 1, 2, 3, 4...
When the exercise starts, follow the same tempo, count from 1 to 8, paying attention to the percussion hits. This will help determine the rhythmic placement of the percussion in relation to the pulse.