This video aims to provide the science behind Pranayama. It talks about what exactly is the purpose behind this respiratory exercise. If done with full knowledge, how it can be beneficial. Also, if there are some ailments, that can be discussed with your mentor so that the exercise does not harm you in any way.
For Techniques of actually doing Pranayama correctly, You can watch:
5 Pranayama You Should Practice Daily by Swami Ramdev (Ramdev Baba)
This is on channel - Swami Ramdev (Ramdev Baba)
Pranayama Ka Sampoorna Package by Swami Ramdev.
This is on channel - Bharat Swabhiman Live