You can't.
Prices are always shown as per night first and by week/month/year if the customer selects them.
Generally prices in the Price Table have to be interpreted by the Customer: as they are they don't mean much. You have to consider discounts, Extras and so on.
So, the best way for a Customer to see the prices is making a search.
If they search for a week, they'll see the total price for it.
Having said that, if this is important for you, please add it to our Feedback and start collecting votes.