Print it upright with the magnet side down (easier to insert magnet).
Add a pause at the right height to insert a round magnet of diameter 8mm and 4mm thickness. (for example S-08-04-N on supermagnete.de)
Mind the magnet's orientation when printing the second one!
I found similar fidgets on printables but you needed to glue the magnet in between 2 parts. This one is way easier.
I printed it in TPU to get a softer touch.
I used adaptive cubic infill at 90%
The author marked this model as their own original creation.