First things first: PC cannot read Amiga disks, Amiga (of course) can read PC disks!
LHA should be copied to your C folder on your Workbench disk or partition since it is a command line driven program.
In a shell you use the command to unarc the archive.
Use the command "LHA ?" to see the help instructions on how to use the command. You will then be able to unarchive the LHA file to a formatted floppy disk for use. (on the Amiga of course)
Alternatively if you have WinRAR you could unarchive the files to a 720k PC formatted disk, then read the disk on your Amiga with CrossDOS but that would be more difficult for a novice user /me thinks!
