Error Sideloading Android L

I am trying to update my Nexus 7 (2013) WiFi to Android 5.0 with adb sideload. I get this error: Finding update package... Opening update package... Verifying update package... E:footer is wrong E:signature verification failed Installation aborted. I have the file (razor). It is a .tgz file, so I entered into the command prompt (I opened inside SDK platorm-tools) and ran adb sideload beaverlog.tgz and it gave me that error (beaverlog is what I named the file). The instructions also said to do it as a .zip file but I couldn't find a .zip file.