Your main cPanel account username and password can serve as your FTP information.
Example:
For Sally, her site is http://sallysite.com
Her cPanel username is: sallysi
Her Password is: IloveD0gs1
Her FTP username would be: sallysi (depending on the client, you may have to use this: sallysi@sallysite.com)
Her FTP password would be: IloveD0gs1
Her FTP hostname would be: sallysite.com
When you use your cPanel username and password, you will have access to your entire account, including home directory files. It is important to be sure you are in the correct working folder inside FTP, which is usually going to be public_html/
Other Accounts
You can also create other FTP accounts that can have specific access to folders that you specify within your account. This can work great if you want to give your developer access to just one folder in your account, or something similar.
To create new FTP accounts, see this KB article here:
http://insty.me/client/knowledgebase.php?action=displayarticle&id=78
Depending on the FTP client, you may have to use the FTP username and append '@yourdomain.com'
I.E. sallyf@sallysite.com
Your FTP Hostname:
Your FTP hostname is the same as your main account domain. I.E. sallysite.com
To create new FTP accounts, see this KB article here:
http://insty.me/client/knowledgebase.php?action=displayarticle&id=78
Depending on the FTP client, you may have to use the FTP username and append '@yourdomain.com'
I.E. sallyf@sallysite.com
Your FTP Hostname:
Your FTP hostname is the same as your main account domain. I.E. sallysite.com