Programming microcontroller with USB AVR programmer

Hello, I'm trying to do the controller mod here: N64 Stick Converter PCB v3 / firmware v3.5 - PCBs available again (August 2017)

Basically you solder an ATtiny24a microcontroller onto a circuit board. Then you program the microcontroller with a USBasp AVR programmer... somehow. From the link:

"After you've assembled the PCB you still need to program the microcontroller with program code provided inside the archive. The N64 Stick Converter PCB got a standard 6-pin ISP interface for programming the microcontroller. Use the .hex and .eep to program both the flash memory and the EEPROM of the microcontroller. Also stick to the fuse byte settings provided inside the archive."

I know pretty much nothing about arduino, so now I'm completely lost. It looks like most people put the microcontroller on a breadboard and plug the programmer into that, but I've already soldered it onto the circuit board. And then after that I don't know how to put the files onto the microcontroller.

I know people who claim to have done this mod but they won't tell me, so I thought I would ask here. Apologies if this is the wrong forum or something. Thanks for your help.

Why didn't You solder a DIL socket and then being able to replace an eventually broken controller?

Railroader:
Why didn't You solder a DIL socket and then being able to replace an eventually broken controller?

First of all I know nothing about this stuff, so I would not have thought to do that. I'm just following the instructions on the page. Second, I'm not sure the socket would fit in the joystick housing.

Okey. 40 years ago I built my own computer finally having some 19 boards 100 * 160 mm, 4" * 6.2". I used Wire Wrap for the connections so sockets where neccesary. Returning 2 pieces of 40 pin failing Western Digital Floppy controllers was easy at that time……

Go on with the programming task! If the controller is alone on the board You can surely make temporary connections for the programming purpose.

Railroader:
Okey. 40 years ago I built my own computer finally having some 19 boards 100 * 160 mm, 4" * 6.2". I used Wire Wrap for the connections so sockets where neccesary. Returning 2 pieces of 40 pin failing Western Digital Floppy controllers was easy at that time……

Go on with the programming task! If the controller is alone on the board You can surely make temporary connections for the programming purpose.

I'm not concerned about anything failing, by the way. I can just solder a new one. (If anything fails, it'll be the potentiometer.)

My problem is I don't know how to do the programming task. I don't know how to connect the wires or how to get the Arduino app (is that what I'm supposed to use? Dunno!) to recognize the microcontroller. Or how to get the files uploaded. If you look at the picture you can see there are six holes in the circuit board that I think are supposed to be connected to the programmer, but I don't know how.

Looking at an UNO board I see 6, 2 x 3 pins, and I believe they are used for programming. Unfortunatly we need to wait for an expert on this. I'm not.

I don't know the Uno for sure, but the Nano definitely has this 6-pin connector.

It's the ISP connector - connecting Vcc, GND, MOSI, MISO, SCK and RESET. That's the primary way of programming the AVR microcontrollers. Just do a search on "ISP programming" and you'll have heaps of resources.

A USBAsp programmer makes this very easy indeed. Connects to your computer by USB, to the board to be programmed by ISP connector.