How to edit the mission area?

Load your mission, press f11, then go to the World Editor Creator (f4).
 Next, click Mission Objects, Mission, and create a physical zone. Then
 switch to the World Editor Inspector. Click on the physical zone
 (if you don't know where the physical zone is, open the folder called
 SimGroup - MissionGroup at the top right corner and scroll all the
 way to the bottom), and change the scale to "1 10 10". Finally, find
 VelocityMod and change it to "-1.5". That should keep you back.

datablock TriggerData (TriggerSwapMission)
{
tickPeriodMS = 100;
};

function TriggerSwapMission::onEnterTrigger(%this,%trigger,%obj)
{

%client = %obj.client;
if(!%client)
{
// return if not a client
// we do not want any npc or other players walking into our trigger 
// and seting off the swap mission
return;
}

%ZoneName = %trigger.ZoneName; // mission name
%SpawnPoint = %trigger.SpawnPoint; // Spawn Point in mission

echo("Zone client:" SPC %client SPC "to" SPC %ZoneName SPC "at" SPC %SpawnPoint);
schedule( 0, 0, loadMission, "starter.fps/data/missions/" @ %ZoneName,false,%SpawnPoint);

}

[b]Don't add this part to the script[/b]

You can ether specify there values statically in the trigger code

%ZoneName = %trigger.ZoneName;
%SpawnPoint = %trigger.SpawnPoint;
eg

%ZoneName = "newMission.mis";
%SpawnPoint = "2";
Or you can set dynamic values on each trigger, F11 > Would Editor Inspector, click on 
the trigger you want to change and add two dynamic value
 “ZoneName” and “SpawnPoint”