This link works for Ubuntu 10 https://launchpad.net/+help-registry/openpgp-keys.html#publish How can I do this in Ubuntu 12.10 because its different in Ubuntu 12.10.
Using the command-line to publish your key you can run,
gpg --keyserver keyserver.ubuntu.com --send-keys yourkeyID
and then you should get the following notification:
gpg: sending key yourkeyID to hkp server keyserver.ubuntu.com
You can check it is present on the server by running the command given in this article:
You can also use the gui program,
Seahorse, to manage your keys, which is the 'Passwords and Encryption Keys' program mentioned in the link you quoted, although you might have to install it now.
A more recent gpg tutorial is available at Ubuntu help, which goes through in some detail how to create, publish, and backup your GPG keys.