Yes. You have to hire the girls. You can't run the store. They have to be there, in the store, to sell stuff.
Think of it like running a campaign, in other games, where you pick a character to place in that slot, and wait for a certain amount of time for them to complete that campaign, then you go back to collect the rewards when the campaign is completed.
Just fill the store, hire girls, wait a day (doing whatever other things you need to do...the girls can be multiple places, at once, too lol), and go back the next day to collect rewards and refill the store.