build an awesome Windows Home Server, too!
Install FilezillaThe first thing you'll need to do is download and install Filezilla Server on your WHS box. It's not a WHS add-in, so you'll need to either use Remote Desktop Connection on your PC or Mac to log into the machine, or just log directly into the machine to do the install. WHS is pretty locked down, so it's probably easiest to download Filezilla Server from your desktop machine, then copy it to a share on the Home Server. (You may need to uncheck the "This file was downloaded from the Internet and may be unsafe" box in the Properties menu for the installer first.) You can choose the default options when installing Filezilla, including the option to install it as a service.
Once Filezilla Server is installed, you need to setup your machine and configure it. First, open the file browser and create a new folder in c: called FTP (or something similar, just don't use spaces, caps, or symbols in the name). Then log into the admin interface (by default, there's no password for the configuration interface) and go to Edit/Groups. I usually recommend setting up FTP servers using groups, most users should have the same settings, and groups let you apply those settings to multiple users quickly and easily. On the right side of the groups pane, you'll see an Add button. Click it, and add a group by typing in a name and pressing enter. I use FTP Users.
Configure the Filezilla Server ServiceFilezilla Server is now setup, but you need to go in and fix the permissions for its service, before you'll be able to connect. On Windows machines, Services are programs that run independent of any user account. They start when the machine starts, but don't require a logged in user. They're great for programs that should always be running, like FTP servers, but by default, services run using an account that doesn't have permission to access the network, which would prevent the server from actually accessing the files on our network shares. Luckily, it's easy to change the service to run as a user account, one that has permission to access network folders.
At this point you should be able to log into your Home Server using a standard FTP client and the username and password you set up earlier from inside your LAN. However, you won't be able to access FTP from outside your LAN, until you configure your router to forward the right ports. We'll do that in the next step.
Configure Your RouterAssuming you've set up your Home Server's *.homeserver.com subdomain already (you should have, it's an awesome feature of WHS), all you need to do to get your WHS machine's new FTP server connected to the Internet is assign a static IP address to it, then forward the appropriate port on your router to the Home Server.
If you're handy with your router's config panels, you can just forward port 25 to your WHS. If you're not, check Port Forward for the proper settings for your individual router. If you don't know your Home Server's IP, it's easy to find. Open a command line and type "ping servername" where servername is the name of your server. The server's IP is the number after "Ping statistics for". It will be formatted x.x.x.x.
Once you've configured port forwarding, you should be able to connect to your home server from anywhere on the Internet. Congratulations!