How do I Import Assets?

I’m very new (about a week old) to Unity and have been following some tutorials to learn the basics, however, every time I try and import packages, as most tutorials instruct, I don’t have access to them. I’ve scoured the Unity documentation, and other third party sites, and all the answers seem to be similar - go to Assets (top menu) → Import Packages, and select the one you want, however, as you can see in the screenshot below, there is only the custom option.

The only thing I’ve done that could be effecting this is saved my project in a different location than the default settings. I’ve also tried downloading earlier versions of Unity, and am still getting the same problem.

Any help would e greatly appreciated.