You can use either the webmail interface or an email client.
You can easily access your WebMail interface by just visiting:
Where yourdomain.com is your actual domain name. If that is not working for you, it might be possible that your ISP is blocking the access to non-standard ports accessed through SSL connection. In this case, simply put:
Where servername.com should be the domain name of your server (ex. http://webmail.siteground121.com)
NB: Please use the full e-mail account username to login to the webmail interface or when setting your e-mail client software. Example: email@example.com instead of you.
Once you login, you can choose between three e-mail programs: Neomail or Horde. Neomail is an easy to use, but more limited web mail client, while Horde is the most sophisticated, but the most functional one.
Select any of the interfaces: if you are logging into this account's webmail for the first time it will ask you for configuration options, like From: field and a signature. Enter your desired options and click Save, and then continue to your inbox.