Select "base" or "install R for the first time" - both of these options will take you to the same page.
Select "Download R x.y.z for Windows", where x.y.z indicates the R version.
If using Google Chrome then the download will appear at the bottom of the browser window.
If using Firefox then click on the down error on the top right corner of the browser window to see the downloaded file.
If using Internet Explorer then there will be a box at the bottom of the browser window that allows you to either run the R install file or save it.
If using Microsoft Edge then click on the down error on the top right corner of the browser window to see the downloaded file.
Install RStudio Integrated Development Environment (IDE) at https://www.rstudio.com/ and click on "DOWNLOAD" at the top of the page.
At the subsequent page, choose to download the free version of RStudio.
The next page, choose to download RStudio that is specific to your operating system or scroll to the "All Installers" section to get the installer file for other operating systems.
Beginning with R 4.0.0, R for Windows uses a toolchain bundle called rtools4. This makes it easier to build and maintain R itself as well as the system libraries needed by R packages on Windows. To install rtools, goto https://cran.r-project.org/bin/windows/Rtools/.