Download R from cran( https://cran.r-project.org/ ) based on Your Operating System.
Here I have downloaded R for Windows. Click "Download R for Windows". Here is the steps for download and Installation.
Click "Download R x.x.x for Windows"
You can see the download file bottom left hand side if you use Chrome
Double click the downloaded exe file and start Instalation.
Select language and Select "OK"
Choose the Installation folder if you want to install other than default folder and Click "Next"
Keep the default option and Click "Next"
If you don't want a different folder name then keep the default name and click "Next"
Keep the default and click "Next"
Double click R.exe and start R
Example of R command