Cannot Build or Install OpenCore on Macbook Air M2

Hi everyone, I want to use my Mac Air M2 to create a bootable USB for my old Mac. For some dumb reasons that, I deleted everything on the old Mac drive, so I cannot run oclp on it. After making the bootable USB, I cannot install OpenCore to the USB because the button is grayed out, like in the picture. I plan to reinstall Catalina, but it might take a while. Does anyone know how to fix it? Thank you