Hello, I joined this forum seconds ago. I want to practice my soldering by making an arduino. I have a question though, how to you get the bootloader on the microcontroller?
You have to use an ISP programmer; if you already have an arduino, it can act as one. It is also possible to use the FTDI chip to act as one (in a bit-bang mode).
Of course, you don't have an Arduino - you are building one, so you need to get an ISP programmer. Its basically a device to allow you to program AVR chips using the ISP (aka ICSP) pins on the microcontroller; it plugs into USB. Of course, if you have such a thing, you don't need a bootloader anymore...
If your starting from scratch on building your own then buying a chip that already has the bootloader installed will certainly simplify your start. Once you have one arduino built then it can then be used to load bootloaders onto new chips. Here is one source:
Lefty