Overlay help (Sniper gun)

So I'm making a mod with guns and I want to add a sniper so I made this overlay: 

https://ibb.co/KGvnq9H    (focus of sniper)

so now I want to make it so that whenever you are using a sniper (ranged item) then it shows this overlay so can someone help with the procedure, I know that this is how to start though: 

https://ibb.co/FKkkhYd

(Player right clicks in air with item
              If item in main hand is sniper

              do:____________________)