Do clients consume dietary supplements delivered online?

Hi. I am Shenza from Boston. I once had a conversation with my boyfriend about dietary supplements and he suggested that I should order it online from websites on the internet. Well, I have never ordered medicines and dietary supplements and I have no idea about consuming it and really want to try it once because of my health problems. I would really be happy if someone here suggested me and guided me whether clients consume dietary supplements that are ordered online or should it be brought from the market ourselves?