Firstly you will obviously need the torrent client utorrent http://www.utorrent.com
If you're very new to torrenting you should probably wait a little while before trying to upload anything and read some posts in the forum about how to get yourself connectable and solve NAT errors first. It is very important that utorrent is not blocked by your firewall (either a separate software one or the windows firewall) or you will not be able to seed your torrent. Also if you have a router you will need to open the port utorrent is using - you can get instructions on how to do that for your router at http://www.portforward.com/routers.htm - it is beyond the scope of this guide.
It is also important that you understand a little about how torrents work. When you download a torrent you are downloading direct from other people like yourself, there are no central servers. People who have a full copy of the files and are uploading them are called 'seeds'. People who have part of the files and are downloading them are called 'leechers' or 'peers'. Peers also upload as they download.
A simplistic representation of how a bittorrent works would be a jigsaw puzzle. When you start to download a torrent you get lots of little pieces of the puzzle in a random order. Your torrent client is sort of like your hands, and the tracker is like your brain directing your hands to where to find the jigsaw pieces.Then your hands (i.e. client) put them back into order. When a jigsaw is finished it makes a complete image, same as when a torrent finishes downloading you have the complete file(s). Unlike with other forms of peer to peer downloading you may have used in the past, generally bittorrent files are NOT playable until they have fully downloaded.
Finally, if you are planning to upload a torrent you must make sure that you will be able to seed it for long enough for people to download a full copy of the files from you.