If you are able to use anonymous ftp, get yourself a copy of
the file README.uploads from the root directory of any
CTAN archive. The file tells you
where to upload, what to upload, and how to notify the CTAN
management about what you want doing with your upload.
You may also upload via the Web: each of the principle CTAN sites offers an upload page - choose from http://www.ctan.org/upload.html, http://www.dante.de/upload.html or http://www.tex.ac.uk/upload.html; the pages lead you through the process, showing you the information you need to supply.
If you can use neither of these methods, ask advice of the CTAN management: if the worst comes to the worst, it may be possible to mail a contribution.
You will make everyone's life easier if you choose a descriptive and unique name for your submission. Descriptiveness is in the eye of the beholder, but do try and be reasonable; and it's probably a good idea to check that your chosen name is not already in use by browsing the archive (see finding files via ftp), or the Catalogue (see finding files via the web).
If it's appropriate (if your package is large, or regularly updated),
the CTAN management can arrange to mirror your
contribution direct into the archive. At present this may only be
done if your contribution is available via ftp, and of course the
directory structure on your archive must 'fit'.