Before captivity by Narakasura

The Bhagavata Purana mentions that the captive women are princesses. The Vishnu Purana says that they are daughters of 

1. gods, 
2. siddhas (saints), 
3. demons and 
4. kings. 

According to the Kalika Purana and the Adi Parva book of the Hindu epic Mahabharata, they were apsaras (celestial female spirits). In the Dana Dharma chapter of the Shanti Parva book affixed centuries later, they are blessed by the goddess Bhudevi to be wives of Krishna.

Some legends narrate that events in their past life led to them being wives of Krishna. A king had 16,000 daughters. While the king was sitting in court with the princesses, Vishnu arrived disguised as a sage. The daughters flocked around Vishnu, making their father angry who cursed them. When the daughters cried and begged for forgiveness, the king blessed them that in their next birth, they would be wives of Vishnu. In other versions, the damsels plead to others for liberation from the curse. The creator-god Brahma, on the advice of his son and divine sage Narada or the sage, himself give the princesses the boon to be wives of Vishnu.

https://harekrishnainfo.blogspot.com/search/label/Narakasura

The Bhagavata Purana describes the life of Krishna's wives after their marriage. Each of the junior wives was given a home, with hundreds of maid-servants. Krishna divides himself into several forms, one for each wife, and spends the night with each wife simultaneously. In the morning, all his forms unite into one body of Krishna when Krishna works as the king of Dvaraka.

https://harekrishnainfo.blogspot.com/search/label/16108

https://harekrishnainfo.blogspot.com/search/label/Chant