1) Start with a session that does not have a managedchrome.com account signed in (I was signed in to my google.com and chromium.org accounts).
2) Go to https://www.google.com/a/cpanel/managedchrome.com/ 
3) It prompts you to pick an account to use - select "add account".
4) You are routed to account manager. Add a managed chrome account there.
5) At the end of the add-account flow, you are left back at account manager (not taken back to the Gaia page from step #3) - this is kind of crappy.
6) Close account manager. Now you see the Gaia page.
7) Gaia page was not refreshed - you are just asked to pick from the same accounts you had before you added managedchrome.com - refreshing this page does nothing.