You can not. If you try, it means you are controlling your bf to be something you want him to be and it is against his self desires. It puts you in a controlling, demanding light who only cares about your needs and nothing about his needs. Control your own self and respect his self.
If he really means anything to you, just be kind and a good friend with no pressure and eventually he will get very comfortable around you and come out of his shell.
If he really means anything to you, just be kind and a good friend with no pressure and eventually he will get very comfortable around you and come out of his shell.