Hi.
If you want to use Windows 7's built-in server, there is a guide on it here:
http://digitizor.com/2009/06/20/how-to-install-a-ftp-server-in-windows-7/
http://digitizor.com/2009/06/20/manage-settings-iis-web-server-ftp-server-in-windows-7/
You'll also need to open port 21 in your firewall.
Be sure you have read all aspects of running av FTP server, since you are opening a path in to your computer from the outside world.
If you want an alternative to the built-in server in Windows, try FileZilla:
Here's a guide to configuring it: