Categories do not show up

I’m very new to wordpress but I am having trouble. Categories do not show up on my site. I’ve made multiple categories, some parented some not, and have 1-2 posts attached to each one. They just do not show up on my site anywhere. I’m using 20 ten theme, since I know that is kind of the basic one, but it is just not working. Is there some secret thing I need to do to get them to appear?