Have you pointed the torrent to the right place?
There's usually a default folder that the client looks in to "see" the files. If it's not there, it can't seed.
The way to check is this:
Double click the torrent. Does it say "downloading" or "checking"? If it doesn't check, the files are in the wrong place.
If so, you may have to start over.
I have one folder for all my torrents (yes, it's huge) so I place the files to be shared in there, make the torrent (save to desktop), upload it (save it to the torrent folder) and open it. It should see the file is already there so just check it and start seeding. Then delete the original torrent from the desktop, of course. Make sure that the default file to save things to (in the client) is the same as where you actually have it. I goofed on that just recently. :-[