Those who observe vrat (fast) on this Ekadashi, and do poojan of Vamanji, will benefit from fruits equivalent to that of doing pooja to Brahma, Vishnu, and Shivji.
During the time of Treta Yug, there was a demonic family, from whom was a King named Bali. However, he was still a dear follower of God. He carried out bhakti, performed pooja on a grand scale, and carried out great yagnas in the name of the Almighty. One day he approached and had a discussion with Indra, which heated up and eventually led to them fighting. Bali emerged as victorious and took over the kingdom of Indra. Indra along with many other Devtas, were very distraught at the actions of King Bali, and came to Vishnu Bhagwan for a solution. Lord Vishnu decided and assured everyone that everything will return to normal and that he will take a form of a Brahmin dwarf so that he could approach Bali and request alms.
Shree Vamanji, took form on this earth, and went to meet King Bali. When Vamanji saw him he asked Bali for alms. Bali, bemused by the sight of a dwarf, in turn asked what he would like to receive. Vamanji calmly replied, "I want to take three footsteps of your Kingdom." Bali laughed at the request, and said, "By all means, take three footsteps." At this moment, Vamanji began to grow to a size larger than that of a giant, and proceeded to take his three footsteps. From his first step, he covered the Earth and the surrounding cosmos, with his second step, he covered the Heavens; and remained his third step. He asked Bali, where he should place it. Bali, renowned for his generosity and charity, placed his head at the feet of Bhagwan. Bhagwan pushed Bali deep into the earth with his third step.
Nevertheless, Bhagwan was still pleased by the devotion and surrender Bali showed. He promised Bali that he will always reside in Bali's kingdom, where later on in time the King installed a Murti of Vamanji. Thus highlights the importance of performing pooja to Vamanji on this Ekadashi.
On the day of Parivartni Ekadashi, Bhagwan continues to rest for the period of monsoon in the middle of the ocean on the head of Shesh Narayan until Kartik Sud Prabodhini Ekadashi. This day carries great importance for those who observe their Vrat accordingly, as it is a day to wash away one's sins.
'Parivartini' means 'of change' and represents the time when Shesh-Shayi Narayan (form of God laying on the serpent Shesh), changes his side and faces the East.
We should all do darshan of Bhagwan and try to give items such as yoghurt, rice and silver coins as alms. We should also try to stay awake through the night, and practice devotion to Shree Hari by singing His glory and keep our utmost faith in him for it is only these actions that can help us in achieving moksha.
This day is traditionally celebrated, by placing Bhagwan in a wooden boat and floating him on water. It is reminiscent of the time when Krishna Bhagwan took the gopis of the village on a boat ride across the sacred River Yamuna.