You can perform a variety of tasks through the Package Manager window:
The procedures described in these sections obscure a lot of the details of what the Package Manager is actually doing behind the scenes. The Package Manager window provides a user-friendly way to install and uninstall packages, by adding and removing packages as project dependencies in your project’s manifest, and then selecting the correct version to install, which doesn’t always match the version you indicated. For more information, see Dependency and resolution.
To open the Package Manager window, navigate to Unity’s main menu and go to Window > Package Manager.