The administration page for the profiler, is located at: Admin > Site > Admin Console, then click Profiler.

When enabled, the profiler adds a little widget to the lower-right corner of the page. For every page render or AJAX request, a button showing the elapsed time the request took is added to the profiler. Clicking on the time will bring up some summary details about the request.

Duplicate queries will be highlighted.

Clicking on the link in the sql column will bring up the queries page showing each query that was executed, it's duration, and a stacktrace showing where the query originated from.