All accounts come standard with either Plesk or cPanel.
Think on this as your Control Panel for your account. All users should login and get familiar with the interface once your account has been provisioned.
To access your panel follow the instruction in your Welcome Letter.
After entering your credentials, the page will load and present you with a multitude of options.
From here you can add email accounts, ftp users, subdomains, install Portal sites, change settings, and much more.
Both panels provide help links for using the software. We will not document anything else here because the documentation is frequently updated.