How to call a function from another script?

Okay so I have a script called MenuManager and I'm trying to tell it to run the function StartServer in my MultiplayerManager script. obviously I'm new to this and I'm following a tutorial but this scripts are in c# and I'm recreating them in JavaScript. I have tried searching for this already but couldn't solve it. so here are the two scripts: (im trying to call the function on line 53)

 // Variables 
 var CurrentMenu;
 var MatchName : String;
 var MatchPassword : String;
 var MatchMaxPlayers : int = 32;
 
 
 
 function Start () 
 {
     CurrentMenu = "Main";
     
 }
 
 
 
 function OnGUI()
 {
      if(CurrentMenu == "Main")
      Menu_Main();
      
      if(CurrentMenu == "Lobby")
      Menu_Lobby();
      if(CurrentMenu == "Host")
      Menu_HostGame();
 }
 
 public function NavigateTo(nextmenu)
 {
     CurrentMenu = nextmenu;
 }
 
 private function Menu_Main()
 {
     if (GUI.Button(new Rect(10,10,200,50), "Host Game"))
     {
         NavigateTo("Host");
     }
 }
 
 private function Menu_HostGame()
 {
     //Buttons Host Game
 if (GUI.Button(new Rect(10,10,200,50), "Back"))
     {
         NavigateTo("Main");
     }
 // Start Server Button    
 if (GUI.Button(new Rect(10,60,200,50), "Start Server"))
     {
 // THIS IS WHERE I WANT TO CALL IT FROM    
         MultiplayerManager.Instance().StartServer;
     }
 //Text boxes and lables    
 GUI.Label(new Rect(220, 10, 130, 30), "Match Name");
 MatchName = GUI.TextField(Rect(400, 10, 200, 30), MatchName);
 
 GUI.Label(new Rect(220, 50, 130, 30), "Match Password");
 MatchPassword = GUI.PasswordField(Rect(400, 50, 200, 30), MatchPassword, "*"[0],25);
 
 GUI.Label(new Rect(220, 90, 130, 30), "Maximum Players");
 GUI.Label(new Rect(400, 90, 200, 30), MatchMaxPlayers.ToString());
 MatchMaxPlayers = Mathf.Clamp(MatchMaxPlayers, 8, 32);
 
 if (GUI.Button(new Rect(425,90,25,30), "+"))
 {
     MatchMaxPlayers += 2;
 }
 if (GUI.Button(new Rect(450,90,25,30), "-"))
 {
     MatchMaxPlayers -= 2;
 }
 
 
 }
 
 private function Menu_Lobby()
 {
 
 }

And here is the MultiplayerManager script:

 public class MultiplayerManager extends MonoBehaviour
 {
     private static var instance:MultiplayerManager;
     
     public static function Instance():MultiplayerManager
     {
         return instance;
     }
     
     public function StartServer()
     {
     
     
     }
 }