First, check that everything is up-to-date. You'll want to commit and push your code, and then run 'bzr status' to ensure that everything is in order.
Now, at a command prompt in the enchanting directory, run a command like this:
bzr export ../Enchanting-0.0.3-Source.zip
You will then have a zip file ready to be uploaded.
Now, log in to launchpad. You will need to create a new release target and can then upload a file to be downloaded. More detail required.
See also: Prepare A Binary Release?