Serial Monitor only prints strange characters

I think i've figured out atleast part of the problem, its that I don't appear to have a 20mhz option on my Arduino Ide. I'm not quite sure how to fix this however

@Prankster Hi, you need to install the NyBoard support in your Arduino IDE. Please refer to the documentation section 4.2.3 at docs.petoi.com.

@Rongzhong Li Thanks for the help! It works now