An ADF file is an image of an original Amiga floppy disk. You can recreate an original disk from an ADF file.
Several methods are available, depending on your Amiga configuration.
Transfer methods
Floppy drive
Kickstart: 2.0 - AmigaOS: 2.1 - RAM: 1.5 MB
Compress the ADF so that it fits on a 720 KB disk instead of occupying 880 KB. Transfer the compressed ADF to the Amiga on a PC-formatted floppy disk. Extract the archive on the Amiga, then create the floppy disk from the ADF.
Null-modem cable
Kickstart: 1.2 - AmigaOS: 1.2 - RAM: 512 KB
Connect the Amiga to a PC using a null-modem cable. Transfer the ADF over the cable, then create the floppy disk from the ADF.
HxC Floppy Emulator
Kickstart: 1.2 - AmigaOS: 1.2 - RAM: 512 KB
Convert the ADF for use with the HxC Floppy Emulator. Transfer it using the SD card, then create the floppy disk using the disk-copy function.