Hitch covers are very easy to install. Most are already assembled. Some of the more extravagant ones will need some assembly, but nothing hard. If they come with bushings, you will put them on the tube cover to create a seal. Then a bolt with a nut or a pin is used to secure it in place. Some will require hooking to the wiring harness.
Here are two videos showing how easy it is to install one. The first one uses a bolt to secure it. The second plugs into the wiring harness so it lights at night, and uses a bolt and pin to secure.