Acting. Sounds ridiculous, I know, but after you have done it a few times it becomes kind of natural.
I have a theory that everyone else is doing it to a greater or lesser degree most of the time.
I was once married to one of those very sociable people that everyone seems to envy. Behind the facade was a very disturbed (and incredibly insecure) individual.
See a therapist. Your personality and emotions can't be easily hacked that way.
tbh talk therapy has never worked for me aside from a slight bump in confidence (knowing someone / even paid / is on my side)