if you haven't done very much in the way of opioids recently, start with one, take another after about 40 minutes if you're not where you want to be. you can always take more but not less and if you take too much you'll just get sick instead of being high.
if you're taking them orally, those are about equivalent to 5mg morphine injected, or roughly 5mg of hydrocodone orally or 3-4mg of oxycodone orally. so they're not very potent and you may want to start with two or three if you have any history of opioid usage.