This will vary if you are on iOS or Android. iOS is called Support Code instead of AMPCode.
- Ensure you have an active and working internet connection on your device.
- Launch the PickCrafter app.
- Make sure you have the Cave biome unlocked
- Navigate to the Options Menu (Wooden Sign at the top right of the game screen)
- Navigate to the Settings Menu (Right-most menu - cog wheel is the icon - https://imgur.com/hrTDrKc)
- Scroll down and tap the AMP Code / Support Code button
- Enter the AMPCode!