You need to open an Online AMD Warranty Request from here: AMD Warranty Request Form | AMD
I believe the Ryzen Processor should have imprinted on it outer metal casing some numbers on it. Input these when you open a AMD Warranty Request plus upload the Amazon receipt that verifies that you are the legitimate owner and you actually purchased the processor plus any other pertinent papers. Also input close up photos of the Ryzen Metal casing with the numbers imprinted in case there is confusion about the numbers you inputted.
You have a three year Processor in a Box purchase from the date you purchased it.
Good Luck!