First of all you will need to "uncompress" or in computer language "unzip" the photos. To do this, try right clicking the folder and there should be an option to, "unzip" this should take a few seconds, depending on how many photos you had zipped. Then when you have your unzipped photos open up your background folder and the folder that holds the new photos you wish to add to your background folder. Now select all of the pictures by clicking the first picture, hold down shift and click the last picture and it should select all the photos that you wish to add to your existing background folder. Now drag those photos to your background folder and you should be set!