What? - Get your QR code pieces from the main page, and try to get the rest of a series from everyone else playing the game.
A series is defined by its colour, red pieces go with red pieces, blue with blue, and so on.
How? - Pester other people in the skirmish discord server who are also in the game. Convince them to share their pieces with you.
Hoarders? - I do expect some codes to never be completed, or to take a long time to be fully assembled.
That's the fun of this, you'll only know what the rewards are if someone (you?) completes a code.
That's also motivation to not hoard your pieces. Probably.
Cheats? - If you can help it, don't ruin the experience with something that's clearly game breaking.
Please, tell me first if you find a critical exploit.