Install Unity Behavior with the Package Manager
To install Unity Behavior using the Package Manager, perform the following steps:
In the Unity Editor, select Window > Package Manager.
The Package Manager window appears.
Open the Add menu and select Add package by name….
Type (or copy and paste)
com.unity.behavior
into the Name field, then select Add.Select Package Manager's In Project context to view Behavior listed under Packages - Unity.
With Unity Behavior installed, you’re ready to explore its features. Next, learn how to add the Unity Behavior sample to your project to start your workflow with ready-to-use assets and examples.