While one FTP account is always created by default once you set up your hosting account, multiple FTP accounts are great if more than one user will be accessing your website's files. You can also restrict the new account's access by allowing it to access only specific folders.
To create a new FTP account, open Websites → Manage, search for FTP accounts on the sidebar and click on it:
At the bottom of the page, you will be presented with Create a New FTP Account section. There you will be able to specify a custom directory, username, and password for your new FTP account:
If you wish for your FTP account to have access to the root folder of your website, leave /public_html as the directory.
Once created, you will be able to either delete your FTP accounts or change their passwords: