All he has to do is click on your name. Or send him your houzz.page.

http://www.houzz.com/user/carolynmckeney

I believe that by default your idea books are public...you have to edit them to make them private. You can confirm by clicking "Edit" then "Settings" (from within an ideabook) to see if you have it set for public or private. Once you have confirmed that it is public just tell your architect your username and s/he should be ale to see your ideabooks.