Go to the Log Viewer under the Admin menu and select "edit log configurations."  Then click on the edit button next to the type of log events you want to be notified of.  Make sure it's selected as "active" and then check the "email notifications" box and put in the info.  I left the default in there which is one in a second I think.

Then go the Host - Scheduler page and make sure the "DotNetNuke.Services.Log.EventLog.SendLogNotifications, DOTNETNUKE" is enabled.  That should be it.  As far as I understand, anytime that scheduler event runs (depending on the frequency you select), it will notify you of any logged events.  So you may see an event logged in the log viewer but you won't get an email until the scheduler event runs.

Hope that helps.