Any suggestions on how to build more charisma/ appear to be more approachable?

I am naturally an introvert and reserved. Many people I am now close to have told me that, when they first met me, I either "appear distant and unapproachable" or "appear too intense to approach" or "seem to be too tough" or other variants like these. I really am a nice and funny person when you get to know me, but I am not outwardly expressive, especially after the military. I want to be more approachable, especially with women.

Any suggestions on how to build more charisma/ appear to be more approachable?
Post Opinion