This is correct that you will see all accounts (created under your reseller account) under Admin CP, but this is just to manage those accounts from this CP.
To manage FTP, web, mail services for an account, you need to get logged into that account (which is your customer's account). You can see an example on http://jodohost.com/stepbystep6.asp , bottom of the page, under Generic Search, use Controls to login into end user's (customer's) CP.
Still, if this is too much confusing to you, then come on Live Chat.