Tension exercises, or dynamic tension exercises, were popularized by Charles Atlas. At its core, tension exercise is strength exercises without using any machines or weights. All the strength comes from one's own body; other muscles are used to generate tension.
The basic principle is the same for every exercise: you create tension in the muscle by using another muscle.
There are plenty of YouTube videos with specific exercises. We suggest creating a small routine to train the muscles you are interested in. Make sure you know how to do the exercise and practice it regularly.
Since you are not using any machines or weights, you need to tense your muscles a lot and put enough effort to achieve your goals.
2 times a week
Practice the exercises with caution to avoid injury.