how do i have a objective list

Questions & Answers
1

like press b to show objectives in game ?

2

Maybe the easy way to achieve this is using OnGUI function. You can read Unity - Manual: Immediate Mode GUI (IMGUI) for detailed explanation to draw texture and text

var isActive: boolean = false;

function Update(){
    if(Input.GetKeyDown(KeyCode.B))
    isActive = !isActive;
}

function OnGUI(){
    if(isActive){
         //Draw Menu Frame
         //Draw List of objective
    }
}