To get to the store by car you must get a permission to transit through the restricted traffic zone of the center of Florence.
It's advisable to leave the car in a private or public parking accessible outside the city center in the area around Porta Romana and Porta S. Frediano.
The nearest car park is the Oltrarno Parking in Piazza della Calza. For information consult the website of Firenze Parcheggi.