once you've got it rendered you should end up with a lot of png images. These will need to be hosted on a web server somewhere. If you've only done a small area, your ISP may offer you some space. Alternatively, look for some free/cheap web space. A quick google turned up http://150m.com/ who will give you 150mb, enough to test with certainly. Once your images are uploaded, add a new repository to maemo mapper with a URL in the format:
http://www.myserver.com/tiles/%0s.png

replace www.myserver.com with the URL of your host, I've assumed you've got all your images in a tiles directory there.

Good luck.