University of Toronto mirror for R: https://utstat.toronto.edu/cran/
Download RStudio: https://www.rstudio.com/products/rstudio/download/#download
If you are having issues with permissions in RStudio when installing or updating packages, you can install R and RStudio without admin privileges. Here is an excellent blog post with step-by-step instructions: https://rpubs.com/tomhopper/windows_nonadmin_install
Download Git: http://git-scm.com/download/win
Instructions for enabling version control in RStudio: https://support.rstudio.com/hc/en-us/articles/200532077?version=1.4.1717&mode=desktop https://cfss.uchicago.edu/setup/git-with-rstudio/