1 - Design the PCB - you can copy the version attached. Note that the push button included on the card (you can see it on the picture and on the PCB) must be removed - there was a design issue with it discovered after ordering a large number of card. The corresponding part has been removed from the main schematic.

2 - Use a PCB assembly company such as pcbway or jlcpcb. It is wise to start with a first sample, many different problems can arise during assembly.

3 - Then you will need to program the attiny1616 chip present on the card. You will find manuals on the internet - the easiest way is to use an arduino board as UPDI programmer, and use the megatinycore library (https://github.com/SpenceKonde/megaTinyCore). Again, you will find instructions on the internet

4 - If you want to play a music that goes beyond "beeps", you will need to use a chiptune routine such as the following : https://github.com/protodomemusic/mmml (this one for attiny85, but you mostly need to slow it down - which will give you the cycles you need to add led effects - and to change the GPIO used to port it to my card).

5 - Led animation synchronized with the tune can be done by adding GPIO activation in the music playing routine. Be aware that all complex calculations must be done before playing the tune if you don't want computation needs to distord your song playing.

6 - The USB plug standard thickness is 2.2 mm. If you want to avoid pay a high cost a non standard pcb thickness, you will need to stick a thickner on the USB plug (If you pcb is 0.8mm thick, the thickner will be 1.2 or 1.6 for example). The best way to do it in large numbers is to 3d print a card holder that help you position and glue very precisely  a "thickner pcb" (5 $ for 7x8 matrix of 12 mm wide rectangkes)