Note: Clicking the links below will take you directly to the download file, which means a pkg will start downloading. I’ve done this to help ease any confusion about which items to download.
Image: After downloading, run the MiKTeX installer by opening the download package
Image: When prompted, choose to install missing packages automatically.
rmarkdown
with RStudioinstall.packages("rmarkdown")
Image: Once you paste the code, you should hit enter.