Am I supposed to get on my uniform at home or at the store?

It might sound like a stupid question, but I recently got hired to work as a cashier at a supermarket. They gave me the uniform and I was supposed to take it home, but I'm pretty sure they said I have to change there? But it doesn't make sense bc they had lockers there, I could have left it there to change into it. I don't know if I'm supposed to take it with me in my bag tomorrow and change into it or what (I'm not sure which tag this applies to, my bad)