Filezilla is an open source project that is comprised of a FTP client program and a FTP server program.
If you want to allow access to files on your computer you must run the server program.
If/When you are connected to the Internet (via cable , DSL, or POTS)you are issued an IP address by your ISP.
If you have a NAT router in between your computer and your Cable/DSL modem, then it receives that IP address and assigns a Private IP address to your computer. The NAT router must be setup to transfer outside FTP requests to your computer's inside private IP address.
When connected to the Internet Click on the Start Button and select RUN, type "cmd" without quotes, click OK, this brings up the command prompt.
Type: ipconfig /all
This will show you your current TCP/IP settings.
Your IP address is shown in these settings.
IF you have a private IP from a NAT router then you will see an address in one of these ranges:
10.0.0.0 - 10.255.255.255
172.16.0.0 - 172.31.255.255
192.168.0.0 - 192.168.255.255
The NAT router provides a hardware protection layer from many Viruses, worms, and Hackers, but it will break your FTP server too. (DO NOT REMOVE IT). If you have one you will need to consult your documentation on how to allow the FTP ports (20 & 21) to translate through to your computer, and how to obtain the IP address.
If the IP address is not in the above ranges then you should get a NAT router and install it, but the IP address listed is the one to give your friend that wants to get/put files from/on your computer.
Note: This IP address may change frequently depending on your ISP, and how often you reboot. Most ISPs let you purchase a static IP address (one that does not change) for $10.00 per month.
You might try these web pages for more info:
http://en.wikipedia.org/wiki/Ftp
http://en.wikipedia.org/wiki/NAT
http://en.wikipedia.org/wiki/Ip_address
Hope this Helps,
Job Cacka