When you're logged in, click on your account, then select 'Secure messaging' in the menu on the left.
You'll be able to see your inbox and click on messages to read them.
To write a message to us, choose 'Create a message' from the menu on the left. Simply type a subject line, put your account number in the box and type your message before pressing the 'send' button.
The menu also lets you see sent and deleted messages.