Welcome to the board. You can't write an amiga native floppy disk with standard PC hardware. You can buy a catweasel controller to drive a PC floppy drive to write amiga disks however, and if you do that a lot it's worth the money.
Before I got a catweasel, I used a program to transfer ADF files to the amiga and write them out to disk. ADF sender comes to mind. It's been awhile for me though, I'm sure some other folks on this board will offer better or more detailed advice.
