How can I stimulate my prostate while I pleasure myself?

Hi,

First get relaxed. Start by masturbating as you normally do, a bit. 

Then maybe use some lube to make it easier and nicer, and insert a finger or two into your anus. 

The prostate can be found a few inches inside the anus. It's round and kind of soft, and on the side facing your front. When you find it, you will know, because there is nothing else similar inside the anus. 

Then for prostate masturbation, just start moving your finger, kind of like the "come here" sign. 

You can also jack off at the same time, but that's up to you. Some guys get a prostate orgasm just from prostate masturbation alone.