In order to make a cleric villager, first you need to make a brewing stand from a blaze rod and three cobblestones using the crafting table. Take out these things from the chest box and put them in inventory, then place them in a crafting table to make a brewing stand. Add this brewing stand back in inventory.
Now you need to find a village to get to a villager. Find an unemployed villager and place a brewing stand next to him. He will become a cleric villager by doing this.