I did the uefi install (full rom) firmware thing and might have messed up

I did the ram flash (forgot what its called) and now im stuck with a flashed chromebook and no way of adding a os to it. i own a hp chromebook 11 g5 ee and the only computer i own most youtube videos say that i need a usb with a os installed on it problem is i dont own a usb

They’re fairly cheap now - all you need is a 8GB to build a Linux/Windows ISO with rufus