Can't find how to post a visitor message

I’ve read the FAQ about how to post a visitor message :

it says “To post a message, click on the ‘Visitor messages’ tab, and use the form at the top of the section”

I find the tab but not the form.
I know any member can switch visitor messages off, so I’ve looked at many members to see if there is a difference, but no.

What am I missing ?

Apparently an admin solved my problem or maybe I just needed to wait for a while.