private message

How can I send a private message to all members Appear after you sign in "only once"

and I want to know who saw the message <img src='https://asprunner.com/forums/file.php?topicimage=1&fieldname=question&id=25438&image=1&table=forumtopics' class='bbc_emoticon' alt=':(' />
How can I do that <img src='https://asprunner.com/forums/file.php?topicimage=1&fieldname=question&id=25438&image=2&table=forumtopics' class='bbc_emoticon' alt=':(' />....