Hi Linda. I merged these two threads because the topic is really the same.
Once you have downloaded a zip file, just double click on it and it will "unzip", so to speak. That is, you will see the files and folders contained within it. Zipping a bunch of files and folders is just a convenient way to send them around as a single package. It both gathers them into a single package and "compresses" them, making the overall files size much smaller, with is handy when you are downloading etc.
So, once you have unzipped the zip file, just takes out the bits you need when you need them. For example, in the chapter 2 folder you'll find the divers-circle.jpg image. Now you can move that image into your site folder so that your web page can find it and display it on screen.