To read your email online, type http://yoursite/webmail or http://yoursite:2095 or 2096 into the browser address window. Input your FULL email address for the user name (firstname.lastname@example.org) and your password for that email account.
To access Webmail from within your CPanel control panel:
Click on the Mail icon.
Click on the Add/Remove Accounts link
Click on the Read Webmail link, next to the account that you want to read.
Note: If you make more than three failed login attempts, there is a good chance your account will be blocked. It's therefore recommended you keep your login and password always available. And if unsure, ask for a reset.