Orient the microcontroller with its outline (labeled U1) on the circuit board, so the circle on microcontroller is on top of the circle on the board.

The indented circle on the microcontroller should be facing the same corner as the dot next to the U1 label on the board.

Align all 44 pins are aligned with their respective pads on the board.

Ensure the microcontroller is aligned both vertically AND horizontally. Once multiple pads are soldered, it is extremely difficult to remove the microcontroller and try again.

Hold the microcontroller still with tweezers and re-heat the solder from the last two steps to solder it to the board.

If you have polyimide tape, you can use it to hold the microcontroller still while you solder the first two leads.