Please note that the code is limited to 2 user cards and is in hex format, so you won't be able to modify anything. This is done so to stop people of using a code for commercial purposes. If for any reason you need more user cards, please send me a message.
After you successfully uploaded the code to your Arduino you need to connect everything as in this diagram:
If for any reason you need to delete user or master cards, you just need to short Digital 2 pin to ground (see EEPROM Reset pins on diagram), and all cards will be deleted. Again first card you will scan - becomes a master card. There is no option to delete cards one by one. So after all cards deleted you will have to program all cards again. You will find a video bellow showing how it looks and works in real life.
If you will decide to make this project, I am more than happy to share some pictures or information of yours on this website. Just drop me a message and I will reply from my email. Hope you will find this useful.