First, you should login to the PEAR website using the account you've been given (see the first step).
Now, finally, you can release your package. This is done again using the convenient web interface. Use the form at http://pear.php.net/release-upload.php.
That's it! Your package has been released, an announcement has been sent to the mailing lists.
Note: You should subscribe yourself to the pear-general mailing list. This, besides IRC, is the first place users of your package will ask for help.