Turn off the shower and let the water stop completely
Unscrew the shower head from the shower arm
Locate the flow restrictor inside the inlet or connector
Remove any rubber washer or screen covering it
Pry out the restrictor with a small flathead screwdriver, pick, or needle-nose pliers
Reinstall the washer and screen if needed
Reattach the shower head to the shower arm
Turn the water on and check for leaks
Confirm local plumbing rules before modifying flow restrictors