From the dashboard, go to “Domains”. Click “Manage” next to desired domain, and scroll down to “FTP Users”. Click the “Add User” button at the top right. After entering the username and password, select the home directory for the level of FTP user access.
Important: If you change your Slamdot account password, the default FTP account password, or server password, will remain the same. You must update the server password if you want them to match (see How do I change my server password?).