I've used the free tutorial videos also available at: http://www.learnmicrosoftbi.com/

You will need to create a free user account in order to view the videos. Also, if you...

If your report is interactive (contains parameters), the statement in the WHERE clause could read something like: where OrderDate between dateadd(dd,-6,@DateParameter) and @DateParameter

Otherwise, you can replace the @DateParameter with...