I think that the method to flash custom ROM or stock firmware into Samsung Galaxy phones is very easy. You only need boot into CWM recovery for flash custom ROM (.zip) or use odin application to flash the stock firmware (.MD5) into Galaxy phones such as Galaxy S2, Galaxy S3, Note 2 and more. Without any step to unlock bootloader, complex command, you can change your Samsung Galaxy phones firmware easily.
As I have mentioned before about the method flash firmware via odin, you need to install Samsung Kies application to enable the odin detect your Galaxy Phone. Samsung Kies application has the USB Driver that enable your Galaxy Note 2 connect to the computer via USB cable. But some of users comment that the odin application still cant detect their Samsung Galaxy Note 2 after install the Samsung Kies application. So, if you also face this kind of problem, then you may try:
1. Restart your computer after the Samsung Application completely install into your computer.
2. Make sure that Samsung Kies application not running when you are using Odin application.
If you have tried both of the method as above and still found that your computer still cant detect your Samsung Galaxy phone such as Galaxy Note 2, then you can try to uninstall the Samsung Kies application. Then Download Samsung USB Driver and install into your computer. Most of users said that odin application can detect their Samsung Galaxy Note 2 after install Samsung USB Driver to their computer. Hope you enjoys!
Download Samsung USB Driver (Windows OS): Link