Installing crown molding in a house is difficult if you've never installed or cut the angles for the crown molding before.
But it's pretty easy to learn by using some scrap wood and learning the angles you need to cut and measure for.
It's hard to explain in words on how to install the crown molding and how to cut the crown molding angles but you can usually find videos online such as on Youtube on how to mark the angles and cut them.
If you're not sure then a good handyman can cut and install the crown molding for your home pretty cheaply or hire a pro and they'll do a great job at installing the crown molding.