OK. I see they neglected to provide instructions for uploading in that tutorial. The problem is that you're using the standard "Upload" process. With your current configuration of the board, that expects that you have a USB to serial adapter (AKA "FTDI") connected to Arduino pins 0 and 1 on the ATmega32A. But you don't have that. Instead, you have an Uno connected to the computer, so it's trying to upload to the Uno. In this configuration, you can upload via the IDE's Sketch > Upload Using Programmer.
However, MightyCore allows you to configure the board for even more convenient usage of the ATmega32A in this situation:
- Select Tools > Board > Bootloader > No bootloader from the Arduino IDE's menus. This will do two things:
- Configure the board definition to not reserve any space in the flash memory for a boot section. Since you aren't using a bootloader, that would only be a waste of precious memory.
- Configure the Arduino IDE so that the "Upload" button actually does an "Upload Using Programmer". This is convenient.
- Tools > Burn Bootloader. This will set the fuses on the ATmega32A for no bootloader.
Now you can just click the "Upload" button to do an upload.