Step 1:
Make sure you have Virtual PC installed with one of the operating systems that is supported by The Sims Transmogrifier (my Virtual PC has Windows 98). Also, you will probably want to have WinZip installed.
Step 2:
Set up a shared folder in Virtual PC that points to the folder on your Mac where you have The Sims installed. Make sure to check the "share every time" box when you set up the shared folder.
Step 3:
Create a directory on the VPC hard drive called TheSims
Step 4:
In TheSims create two more directories, one called GameData and one called Downloads
Step 5:
In GameData create a directory called Objects
Step 6:
Using the shared folder you set up in Step 2, find the Objects.far file from your Mac version of The Sims. From the folder where The Sims is installed, you should go into GameData, then into Objects, and it should appear there. Copy Objects.far into the Objects directory you created in Step 5.
Step 7:
If you have any of The Sims expansion packs (Livin Large, House Party, etc) you will also want to copy the .far files from the expansion packs into the Objects directory you created in Step 5. The Livin Large .far file can be found in the ExpansionPack folder of the folder where The Sims is installed.
Step 8:
Copy the Sims Transmogrifier .exe file into TheSims directory you created in Step 3
That's it. When you clone an object, the cloned objects .iff files will appear in the Downloads directory you created in Step 4, in a subdirectory called Transmogrified