Thank you for getting the game! To access the accessory store to buy stuff you first have to work at the accessory store part-time on the weekend. And to get the third dates with Pran he needs to be your official boyfriend. You do that by reaching the two heart affection bar and filling it up completely. Then you can open the date screen and there will be a new button in the bottom right corner. That will let you ask him to be your boyfriend. I hope that helps ^^