This phrase means to pay someone to do something for you. Typical examples are:

• getting your hair cut
• getting your clothes dry cleaned
• getting your oil changed
• getting your nails done

Use one of these phrases whenever you're talking about one of these kinds of services:

Hey! Did you get your hair cut? It looks nice!

I always get my shirts cleaned at this great place on 35th Street.

(Talking about taxes) I'm getting them done by a real accountant this year. It's just too complicated to figure out on my own.