Go to your device's settings and set the date to before 2012.
Step 2: Website
Go to coolroms.com on your device.
Step 3: Emulators
Click on the 'emulators' category.
Step 4: Device
Select the device your using.
Step 5: NES
Scroll to Nintendo category an select 'John NES'
Step 6: Install
Step 7: Set Date...again
Go back to settings and set the date back to the current time.
Step 8: App
Open up your new emulator.
Step 9: Get Games
Click the three dots and then click on 'find games'. Download any NES game you want and then go back to your emulator and click 'search games' this will automatically find any downloaded games. Enjoy!!