How to add drop-down menu items?

I have searched and found a few things addressing this, but they seem to be outdated for WP 3.5.

Anyhow, I have just moved to WP, and am running the Graphene theme. My site is http://acupfulloffaith.com/.

My trouble is this: I’d like to add a drop-down item on the menu bar that is linked to a certain category (“Reviews”). I’d like it to drop down with options for the child categories under Reviews. I have tried adding the Reviews category to the menu by itself, and also tried adding all those categories. No matter what I do, they don’t show up. I have tried refreshing the page. If someone could please tell me how to do it (especially if it doesn’t involve tons of coding!), I’d really appreciate it! Thanks!