Drink 6 cups of water over the course of an hour or so, go for a piss twice and make sure you're very hydrated. After that, masturbate for at least 40-60 minutes while 'edging'. Edging is when you masturbate until you almost reach climax, but then stop. Let yourself rebuild and keep going. Repeat the edging process as many times as you can but do it at least 4-5 times. Take a short 20-30 second break, and get ready for the cumshot of your lifetime. The last step, you need to masturbate as hard as you possibly can. Squeezing your penis and holding in your load for as long as you possibly, until you just can't hold it in anymore. Just before you cum, squeeze your penis and push and push.... let that thing EXPLODE!!!
You need to believe that you can cum as far as you most possibly can, and you'll become a shooter in no time.
That's as detailed of a process as I can give you. Myself, I blow it, every single time. With that process I've ejaculated as far as 7 feet at times. I've missed my girlfriend's face and shot in on the walls behind her. But that's just me, I know that sounds kind of gross but I love to shoot my cum. You'll be shooting though, maybe not as far as me as everyone is different, you just need to believe in yourself and blow that load!!