Either from the event bulletin or from the event preview on the All Rooms screen, tap on the event that you want to add. A half-screen will pop up showing you the option to:
- "Share" - generates a link you can forward or copy and share via message or e-mail
- "Tweet" - drafts a tweet with the event title, hosts, and link to the conversation
- "Copy link" - copies the event URL to your clipboard
And, of course, there's always the option to tell people about it the old fashioned way!