Megan, if you open up AnkiDroid and tap the 3 dots on the top right to bring up the menu, you will have an option to import. A popup will tell you to place an APKG file in a specific directory. What you need to do is extract the zip file you downloaded, it will contain the APKG file, then move that to the directory which was on the popup. Open up AnkiDroid and go to that import option again and it will automatically import everything you placed in that directory.