Press [ Ctrl ] [ Alt ] [ T ] to get to the crosh shell prompt on the chromebook (See first image). Note: these first 3 shell images were captured via cloudready which is a chromeos workalike not an actual chromebook but are identical for our purposes here.

Use the "shell" command to get to the shell prompt. Just type "shell" into the prompt and press enter (see second shell screen image).

Type the following (or cut and paste into a single command line... see third shell screen image). I include the full command in the next bullet point...

cd; curl -LO https://mrchromebox.tech/firmware-util.sh && sudo bash firmware-util.sh

Press enter on above command line when you are ready to start converting your chromebook to a fully functional general purpose personal computer.