When you create a meeting, there is an "Invite Others" button at the top of the meeting. If you click the button, Instant Agenda copies a meeting link to your clipboard. You can then paste this link into an email, document, or calendar invite. You can print it out and tie it to a pigeon's leg, if that's your thing—how you distribute it is up to you.
See also -- "Does Instant Agenda integrate with my calendar?"