There are several ways of doing this. I use a relatively simple method. Go on Ebay and get a cable (XM1541 or some variation thereof). It will run you about $15+shipping. Download software called "opencbm" and install it on your favorite PC with a parallel port. (The cable goes from PC parallel port to commodore disk drive serial port). Hook the IEC serial end into your 41/71/81 and you're set to go. opencbm is command line based. You can probably find a nicer GUI out there - but opencbm is simple and gets the job done.
Good luck!