Please be advised that most of us don't recommend people buying unweaned babies. For any breeder or shop to sell off an unweaned baby to someone who don't have the slightest idea on how many time to feed or the amount, even how long to go through the process is bothersome. All that question should of been asked before you decide to bring them home. Please do visit the link that Wendy provided above!!! Hand feed slowly if you must, do not rush as you can aspirate baby birds easily.
At that age I would advise on feeding 4 times a day, this was my time schedule when I used to breed, 6am, 12pm, 6pm, 12am, they would be ready to start climbing around in another week.