1) Login to Webmail and click on Roundcube.
2) Click on the Refresh button on the top left to check on new email.
Your Inbox will have a number listing any new emails, (you will not see a number, if there are no new emails).
3) Click the Inbox button, to ensure you are looking at the correct folder.
4) You will see any emails in your Inbox listed to the right.
Double-click the email to read the contents.
You will then be able to read the contents of the e-mail.
There are buttons available on the top, for common tasks such as Replying, or Forwarding the email.