Can you make sperm come out?

It's called 'semen' (see-men) and it has sperm in it. The semen can be made to come out forcefully during an ejaculation, part of the sex act.

If you can not ejaculate yet it is probably because you are not old enough and haven't got that far in your development yet. it usually starts around pre-puberty from the age of 10 and around. That is when semen can come out but semen does not contain sperms until you have reached puberty.