The feature only works if you are all on the Exchange Server.
Make sure that the "Public Folders server" entry under the "Advanced" tab in
your account settings (Tools > Accounts) is correct. You might want to try
adding /public to the end.
Then, in the new event, address to the Exchange Server user, and click the
"Scheduling" tab. You should then be able to see the user's free & busy
time blocks.
