Go to Catalog>View Products
Check the boxes to the left of each product you wish to update or the upper left box to select all products on the page.
Click on the Actions button and choose Bulk Edit Products
There are two methods to update products in bulk.
Make the necessary changes to each product and click the Save & Continue or Save & Exit button.
Click on the Bulk Actions button to open the Bulk Update Actions menu.
Enter the information you want to update and click the Update All Products button.