Can a 13-year-old boy masturbate? And how?

Both boys and girls masturbate by touching there genitals from a very young age, most boys and girls start to masturbate properly by the age of 10 even though boys don't normally produce semen untill around the age of 12 they can still have what is called a dry orgasm.

When you get an erection hold it in your hand and wrap your fingers an thumb around the shaft and just move your hand up and down the shaft, what speed you go is what ever feels good for you. Most guys start slow and build up speed as they feel themselves getting closer to ejaculating. The way you masturbate also depends on if your circumsised or not too as most circumsised guys find it's easier to use lubricant as they don't have the lose skin to slide up and down the shaft, some guys who still have a foreskin like to keep the foreskin over so it pulls back and forward on each stroke while others like to keep it back so they rub the sensitive glands as they stroke back and forward.

Just experiment and do what ever feels best for you, if you have any more questions feel free to ask.