1. Download and extract a zip file containing your desired firmware.
2. Open Odin Tool.
3. Boot your device in the "Download Mode":
Press Volume Down, Power and Home buttons at same time for 5-8 seconds until download mode is active.
4. Connect your device to PC via the USB cable while in download mode.
5. Next, check the "Auto Reboot" and "F. Reset Time" options in Odin Tool.
6. Hit the AP/PDA button then browse and select a tar.md5 file from the extracted folder.
7. Finally press the start button to begin flashing the firmware update on your device.