Installing an Arduino Bootloader
Uploading Code - Easy Way
The easy way to upload the bootloader involves using the Arduino IDE. Open your IDE select the board you want to program. Then select the programmer (if you are using the Arduino as ISP you will also need to select the COM port that the Arduino as ISP is connected to). Then select BurnBootloader. This will take the board you selected and look up the associated bootloader in the board.txt file. Then, it will find the bootloader in the bootloader folder and install it. This only works if the board is installed correctly in the IDE and you have the correct bootloader.
If for some reason you want to use a bootloader that isn’t installed in the Arduino IDE, visit the nest section. However, it’s probably easier to just install the bootloader from the Arduino IDE. For those who are curious about settings such as fuse bits, have no fear. Arduino takes care of all the messy details for you when you burn bootloaders through it.