With your left heel, press down on the Yoni. Keep the right heel squeezed against the space just above the generation organ. Draw the Apana Vayu upwards by contracting the anus. 

Mula Bandha is the name for this. The Apana Vayu, which is responsible for excreta ejection, has a natural propensity to shift downwards. 

The Apana Vayu is forced upwards by the practice of Mula Bandha, which involves contracting the anus and forcibly pulling it upwards. 

The Prana Vayu is joined to the Apana Vayu, and the Prana-Apana Vayu is directed into the Sushumna Nadi. 

Then the Yogi \sattains perfection of Yoga. The Kundalini has been reawakened. The Yogi consumes the Immortal Nectar. In Sahasrara Chakra, he loves Siva-pada. 

He receives all of the holy Vibhutis as well as Aishvarya. Anahata sounds (mystical inner sounds) are heard clearly when the Apana is united with Prana. When Prana, Apana, Nada, and Bindu come together, the Yogi achieves Yoga perfection. This is the highest point that can't be achieved on the first try. This can be done over and over again for a long time.

The use of Bandhas and Mudras aids in the attainment of Siddhi in the practice of Pranayama. Mula Bandha helps to maintain perfect Brahmacharya, provides Dhatu-Pushti (nerve vigour), relieves constipation, and boosts Jatharagni. Mula Bandha should be used in conjunction with focus, meditation, Pranayama, and all other Yogic Kriyas.

You may also want to read more articles on Yoga and Holistic Healing Here.