Here you can add new email accounts. The drop down arrow will show your principal domain name and any domain names that have been added with cpanel under Add On Domains. Simply select a user name and password after setting the dropdown arrow to the proper domain.
If you expect a lot of mail to a particular address you can raise the mail quota. In most cases you should not set it to ‘unlimited’ as a precaution against malicious DNS attacks.
If you are a two or three person business you will want an account for each employee or partner who deals with customers, but even a one person business can benefit by adding accounts for specific purposes.
For example you can have one email address for basic customer service, one address for priority service for your largest customers, and one for product returns. If you are in a service business you may want a separate email account for each project, so you don’t have to search through a lot of unrelated mail to see what a client wanted when you reach that stage in their project.
If your email will be used by multiple people then be sure to build them with different passwords. If you will be the only user you may use the same password for every account. If you will be accessing the email accounts while logged into your cpanel you will not even need to use the passwords to access the mail through the web interfaces. For security reasons do not use your cpanel user name as an email address (the same holds true with any WordPress administrative user names).
Note that you can also forward all the email to an account you are already using such as Gmail, or Yahoo. By looking at the account they were forwarded from you will instantly know the topic.