Establish a design idea for your fidget spinner. Then find a way how you would like to make your fidget spinner. I made mine from a 3D printer.
If you are creating your fidget spinner from a 3D printer then you would need to go on https://www.tinkercad.com/ To find a fidget spinner design you like.
Print out your design from https://www.tinkercad.com/
you now need the bearings to put on the fidget spinner. You can get the bearings from online or at a hardware store that has them.