Unity Standard Assets and items on the Unity Asset Store are supplied in asset packages. Asset packages are collections of files and data from Unity projects, or elements of projects, which Unity compresses and stores in one file with the .unitypackage extension. Like a zip file, an asset package maintains its original directory structure when it is unpacked, as well as metadata about assets (such as import settings and links to other assets).
Starting from Unity 2020.1, the dedicated Asset Store window is no longer hosted inside the Unity Editor. However, you can still access the Asset Store website at https://assetstore.unity.com/ and you can still search for your purchased and downloaded Asset Store packages, as well as import and download them directly in the Package Manager window.
To purchase an Asset Store package from Unity or a third-party publisher, start by searching the Unity Asset Store to find asset packages that meet your needs. When you find an asset package you want to use, purchase or download it in the Asset Store. You can also make it easier to locate packages by organizing your assets with labels and hiding Asset Store packages that are deprecated or unused.
在 Unity Package Manager 中，选择 My Assets 筛选条件以查看您可用 Asset Store 资源包的列表。可按名称搜索 Asset Store 资源包。找到要使用的 Asset Store 资源包后，可将资源包下载并导入到 Package Manager 中。如果 Asset Store 资源包具有可用的较新版本，也可以直接在 Package Manager 窗口中对其进行更新。
To create your own (custom) asset package, you can:
To import a local custom asset package into your project:
You can use the Package Manager window to manage your Asset Store packages within your project. However, if you need to access your asset files directly, you can find them in the following paths:
~/Library/Unity/Asset Store
C:\Users\accountName\AppData\Roaming\Unity\Asset Store
这些文件夹包含与特定 Asset Store 供应商对应的子文件夹，并在下载和导入后变为可用状态。资源文件以 Asset Store 资源包发布者定义的结构包含在子文件夹中。