If Grassy makes 2 more posts (just say "Hello", "Thanks" or anything!

) they will then be able to use the Private Message (PM) system within RootsChat.
On the thread, underneath the poster's avatar, you will see a document icon.
This is green if they are currently online, white otherwise.
Click on that to take you into the PM system.
You can exchange email addresses there; or just chat.
You can't attach documents, though.