Did you use the search option on this forum?
This has been discussed recently.
Anyway... here goes:
To start using pc floppies on your Amiga mount pc0:
To mount pc0: go to Storage/Dosdrivers on your Workbench partition (or on the WB Extras disks). Now you can read and format pc floppies. Use your Amiga to format the disk to 720K. Then you can use the floppy in your pc etc...
By the way WinXP can format 720K this way: format a:/n:9/t:80
Oh and I see the next question coming. You need to download lha to unpack the archive on your Amiga unless you use OS3.9. Look for it on
www.aminet.net Read the docs for the usage. It's really not that hard.