Hi Chris,

When you create an ideabook, it will automatically come up on your profile feed. Users will be able to see it as long as you don't make it private.
To share with a specific User on Houzz, click Collaborate which will be at the top of your ideabook and type in the User's name or e-mail.
And finally, if you'd like to share it outside of Houzz, you can e-mail it via the E-mail tab at the top, or click on one of the Facebook/Twitter/G+ icons to share it on the appropriate platform.

Hope that helps!