Welcome.
The "PM" option should appear for you in time after you make a few more posts.
You MIGHT be able to unlock the function by becoming a supporting member.
Copied from a post I made about a year ago:
When available, PM's are started as
conversations by clicking the arrow-ish icon next to the bell (notifications) at the upper right hand corner.
Minimum posts to change avatar, etc. I think is eight or so. ( plus perhaps a time element? )
vs
Kind Regards and good luck.