need help writing to disc

[Dy7SLyTq]

so im trying to write my own environment starting with my own bootloader then an os, then a language for it. im not looking for tips or anything just a little bit of background. anyways i have a basic hanging bootloader that compiled fine with nasm, but then i have to use the dd command to write to disc (well a floppy but considering i dont have a floppy disk or drive im using a cd). its a cd in my drive, but i dont know how to write to it. i was using dd if=boot.bin bs=512 of=/dev/fd0 but the location at the end isnt the location of the disk