Soo its pretty simple how a cooldown works.
In your onItemRightClick method you would want to do something like this
private int coolDown = 0;
@Override
public ItemStack onItemRightClick(ItemStack itemstack, World world, EntityPlayer player) {
if(coolDown <= 0) {
player.motionY = 2;
coolDown = 100; // Cool down time in ticks
}
}
Then you will need to override the onUpdate method allowing the cooldown to count down.
@Override
public void onUpdate(ItemStack itemstack, world world, Entity entity, int i, boolean B) {
if(coolDown > 0) coolDown--;
}
Soo yeah, Its pretty simple all your doing is making it count down in ticks so a player cant use it. You will want to add a if() statement to see if the cooldown is completed so the player can use the item again.