In order to connect to FTP to upload your website, you simply use ftp.yourdomain.com with your cPanel username and cPanel password. This will give you full access to upload your files.

If you need to create a secondary user, you can do that by first logging in to cPanel (generally www.yourdomain.com/cpanel). Once logged in select FTP Accounts found under files. You can then add a user and create them a password. If you would like to give them full access to all files leave the directory field blank. It's also recommended keeping Quota as unlimited unless you're wanting to restrict how much storage this user can use in a specific folder. 

Keep in mind any user you create will login with the username that you create @yourdomain.com. So for example if you created the user joe, their username would be joe@yourdomain.com. This does not create the user an email address, that is simply an FTP login account.