Working at departmental stores does not include only salespersons. There are various designations in a departmental store, though it is true that the majority of the employed work as salespersons.
They help the people with locating and selecting items, selling goods, setting the shelves, etc. there is no formal education required to apply for a job as a salesperson at a department store. Once they apply, they go through a training period and then they are employed.
Many people do it as a part time job. The other designations are that of the store manager, sales associate, customer service manager, and cashier. There are also many other people involved, but these are the main posts.