Story of Vaikunta Ekadasi is mentioned in the Padma Purana. The Purana indicates that Bhagvan Srihari Vishnu took the form of ‘Ekadasi’ – female energy – to kill demon Muran. This happened during the month of Margazhi (Dhanur Masa). Impressed by ‘Ekadasi,’ Vishnu told her that whoever worships him on this day will reach ‘Vaikunta’ (heaven).
Like all other Ekadasi days, devotees fast on Vaikunta Ekadasi and observe vigil the whole night. Some people indulge in meditation, Japa and singing of Hari Kirtan.
Rice is avoided during Ekadashi days as it is believed that the demon Mura finds a dwelling in the rice eaten on Ekadasi day.
Vaikunta is a symbolic place. In reality Vaikunta does not reside outside. But it is here in us. Realizing this we attain Vaikunta.