You can send a message or an invitation to chat to any user at any time, whether he or she is online or not.
Simply go to the Community page and click on the "Say Hello" button on the user's profile card. You can also use the Filters on the Community page or select the "Find my match" button to find partners.
Type your message into the provided text box and send it to your partner.
If you have a message from another user, the globe Notification icon will contain a number in red. Click on that icon to access your messages. You will also receive an email message notifying you about the message, unless you choose to not receive messages (Account Settings > Settings > eMail Preferences).