There are three ways you can access the Unity Asset Store:
- Open the Asset Store window by selecting Window→Asset Store from the main menu within Unity.
- Use the Shortcut key (Ctrl+9 on Windows / ⌘9 on Mac OS)
- Browse the web interface: https://www.assetstore.unity3d.com/
You may be prompted to create a free user account or sign-in if it is your first time accessing the Unity Asset Store.