How do I add an ftp user?

Alright I have been looking over the information on the website and I found how to add a user to my account, but it shows them not using the same 2400mb I already have. So i went ahead and deleted that account immediately since I wasn’t sure if i would be charged 2x as much. Pretty much what i want to do is make another login and password for a subdirectory of my webpage. So say my webpage is and i wanted another ftp logon/password to have full access to say The reason for this is I want to give access to somebody to post some pictures and documents on the website but I don’t want them having full blown access to my files. Oh and I don’t want to have to pay anything additional over what I’m already paying. Thanks.
I don’t work here. I’m just your typical support forum volunteer.