it is not so hard!
You simply:
1-plug your drive to your PC
2-Run WinUAE with the -disableharddrivesafetycheck command line option
3-Add the drive to WinUAE (Add Harddrive)
4-Boot your WinUAE with the workbench installation floppy and continue from there.
5-Remember to set the correct parameters in HDtoolbox for partitioning your drive (as mentioned in the guide)
But then if you are using a drive bigger than 4GB you need a patch (the guide explains how to do this).
That is basicly all there is to it.