How do i approach my optometrist and ask him if i can volunteer or intern at his office?

i'm thinking about pursuing optometry and i really need some experience in an office. im going to be a senior in high school next year and i really need to step it up if i want to get into a good college. i was thinking about volunteering or interning (idk if there's a difference) at my optometrist's office. can u just walk in and ask or is there an application you have to fill out? i've never done this before. i'm not asking for much. maybe just start off low like take out the trash or file folders or write mailing addresses. i've done it before at my brother's office.