After login your account you can send email message from the 'My Account' page. Click the 'Send Message' link. In this page you can write your message, and then click 'Send' button.

You can also send an email message to any member from inside that member's profile page. The 'Send Message' action link is located in the member profile page too. You can send an email message to any member whose profile appears in the 'Search Results' page. The 'Send Message' action link is located in the top of the member profile.