In that ZIP file you should find two files one is the X-Carve PP for Inches and the other is the X-Carve PP for mm
You need to extract those two files and put them somewhere that you can find them.
Open your copy of VCarve and under the File Menu click the “Open Application Data Folder” item
A file explorer window will open that looks like this
Open the directory named “My_PostP” and copy the two X-Carve post processor files into it.
Now when you save a toolpath you will have the option of picking which of the two X-Carve Post Processors (Inches or mm) you want to use. I always choose inches.