This exercise need privacy. Stand against the wall with your penis upward, the underside of the penis touching the wall. Bend your knees so that your scrotum touches the wall. Touch the wall with the tip of your tongue. With your fingers of both hands you softly rub or tickle your nipples. Focus your attention on the tip of your penis. (women could focus on the clitoris or vagina) and say in your mind, 'Fill me with your creative power' or 'Fill me with your life-giving power'. Don't think of the words. Don't think of anything. Try to focus your attention fully on sensation on the tip of your penis. If you get distracted, focus your attention again. It you feel any pleasure, allow yourself to enjoy the pleasure and relish it. Get rid of any inhibition. If you don't get any pleasure, don't worry about it. If you get an erection, let it happen; accept it and be happy about it. but if there is no erection, don't worry. Don't compare today's experience with yesterday's. Totally avoid performance anxiety. What happens today is good for today. Practice regularly for 15 minutes every day.
Alternatively you can focus your attention on your nipples or the tip of your tongue. These are also pleasure zones.
With regular practice you will get a tremendous pleasure on the tip on your penis. You may also come to the point of ejaculation. But stop before you reach the point of no return. If you can acquire ejaculation control you can prolong this exercise for very long time.