SceneManagement error

I’m trying to access SceneManagement in Unity 5.3.4f1 but keep getting the error

Assets/scripts/enchendo.js(1,8): BCE0021: Namespace ‘Unity.SceneManagement’ not found, maybe you forgot to add an assembly reference?

I’ve tried putting the script import Unity.SceneManagement; at the top of my .js but I still get the error. How can I fix it?

The namespace is UnityEngine.SceneManagement, not Unity.SceneManagement