You can't change who you are at the core. I am an extreme extrovert.
My coworkers tease me for being so talkative. At the core, that is who I am and I am ok with it. My husband is an extreme introvert. He will never be like me, being able to strike up a conversation with a random stranger.

They say the art of conversation is about asking questions about the other person and listening. Smile a lot, even if you don't feel like it. Look people in the eye. It can be uncomfortable, but focus a point between the eyes. It gives that same impression. Even if you don't talk a lot, practice your non-vocal communication.

Hope that helps!