1. I assume you have read and adopted the better way to update R
2. Make a folder c:\program files\r\library\Mplus
3. Download mplus.r to that folder
4. Do a google search on "how to make an R package", skim this, and give up.
5. Instead, just run "> source("c:/program files/r/library/mplus/mplus.r")" when you want to call the embedded functions