Having a RW_LEGACY OS be stored in the main drive / without USB?

I tried to get rid of the write protection screw but I don’t have prying tools at home.
So the next best thing was to be able to boot into it without having to use the external drive since I want to use it for other things after it’s installed. In the installation menu it only display the drive, so I’m not sure what to do about it.

RW_LEGACY, like the rest of the firmware, is not stored on the internal storage drive, but on a separate SPI flash chip.

I’m not sure what you’re asking exactly