Network Manager Script Error BCE0018: The name 'NetworkManager' does not denote a valid type ('not found').

Hi, im working on a 2D multiplayer game in UnityScript. I started trying to use the Network Manager but on all the tutorials i found it showed adding a Network Manager component in the network tab, but i can't find the Network tab or the Network Manager component. i searched the Documentation, and i found out that the new Network Manager is a script, so i copied the script but i got this error:

Assets/Scripts/Multiplayer/NetworkManager.js(2,30): BCE0018: The name 'NetworkManager' does not denote a valid type ('not found'). Did you mean 'UnityEngine.NetworkConnectionError'?

Here's the script:

#pragma strict public class Manager extends NetworkManager { public override function OnServerConnect(conn: NetworkConnection) { Debug.Log("OnPlayerConnected"); } }

I tried searching to see if anyone else had this problem, but i couldn't find anyone else who had this problem. Does anyone know how to fix this?