Select ui slider to change float value?

Hello i have a slider in my scene and i want it to change a float value from 1 to 3. But i dont know how to do this. If you can tell me how please do so, and use pictures! Thanks.

here is my code if needed:

 var Crosshair1 : GameObject;
 var Crosshair2 : GameObject;
 var Crosshair3 : GameObject;
 
 var SliderValue : float;
 
 function Update ()
 {
         //crosshairs
     if(SliderValue == 1)
     {
         Crosshair1.SetActive(true);
         Crosshair2.SetActive(false);
         Crosshair3.SetActive(false);
     }
     
     if(SliderValue == 2)
     {
         Crosshair1.SetActive(false);
         Crosshair2.SetActive(true);
         Crosshair3.SetActive(false);
     }
     
     if(SliderValue == 3)
     {
         Crosshair1.SetActive(false);
         Crosshair2.SetActive(true);
         Crosshair3.SetActive(false);
     }
 }
 
 //crosshairs
 function ChangeToCrosshair1 ()
 {
     SliderValue = 1;
 }
 
 function ChangeToCrosshair2 ()
 {
     SliderValue = 2;
 }
 
 function ChangeToCrosshair3 ()
 {
     SliderValue = 3;
 }