PAC-MAN MUSEUM+

When in your arcade, press then select 'Customize' then select a square with some space (the partitions take up 2 spaces each). Use / to select the 'Decoration' tab to choose a partition. You'll need to place all 4 different partitions in to your arcade at the same time and exit the menus back to your arcade to get the achievement to pop (there is a slight delay before it does).

Here are the 4 partitions, the game they're awarded from and how to get them: -

Polka Dot Partition - Pac-Man BattleRoyale - Eat ten fruits in a game (Eat dots to get the fruits to appear. Avoid eating the other player and try not to die.)

Cyber Partition - Pac-Man Championship Edition - Get a score of 100,000 in Championship Mode

Happy Partition - PacMotos - Clear 5 stages in 1 game

Geometric Partition - Given to you at the start of the game and will already be in your arcade unless you removed it.