The correct "process" to using FTP to access your system's hard drive was new to me also. I had never done a "mod" like this before on a system that was this dependent on network. I mean, on Wii there is always wifi, but you could do without it, and on ps2, well, you just threw stuff on a flash drive and booted your little "mod" off of a memory card.
Anyway, you didn't come here to learn about the history of modification. What you do is you find the IP address on the network of your box, then open My Computer, or Windows Explorer (same thing, slightly different "shell"), and type it in like this (but replace the words "ip address" with your box's IP address):
ftp://"ip address"
It will most likely ask you for a username and password. Unless you otherwise adjusted it, it will NOT be anonymous. The default for many xBox Dashboards is "xbox" in lowercase letters and numerals for both the username and the password. From here, you're in. Each "lettered folder" represents a drive letter on the system (should seem familiar to your Windows xp or 7 desktop/my computer area).
Good Luck!
- 2 Bunny