Best way would be to just use WinUAE if you have a PC, but you can take the files and zip them using split mode. Split the files in half and put them on a 720kb disk. Copy the zip files to your A500 RAM disk and then unzip them and use transADF to write it back to an Amiga disk. No easy way to do it.
2nd way.
Use a null modem cable from your PC to the A500. Using a terminal program on both computers connect and "upload" the adf file to the A500 RAM drive again and do the sme thing. If you only get an A500 with 512kb of RAM your screwed because it just wont work.