You can use either the webmail interface or an email client. If you need help configuring email clients, please visit the step-by-step guides for configuring MS outlook and Mozilla Thunderbird.
We have found the the Mozilla Thunderbird email client is one of the easist to get going and use.
Or you can easily access your WebMail interface by just visiting: http://www.yourdomainname.com/webmail, where 'yourdomainname.com' is your actual domain name.
When you do that you get to the next screen you will see this:
In above screen, enter your email address and you password then click login.
You will then see the below screen:
You can choose either of the three email clients to read, send or store your email from any computer.
On this screen you also can change your password and configure your computer based email client.
If you are going to use the server based loging to check and handle your email, we have found Horde to be the most user friendly online client.
You can Google how to use Horde and get lots of tips.