Downloading R into a computer is straight forward. The web page r-project has instructions on how to download. Below is a recent video by Tech Related Tips from YouTube for the first time users to download R and Rstudio (see below).
Download R for Windows
It is possible to use R without a script, however an editor is needed to record every steps in an organized manner. One of the simplest editors comes within R, open R, click File and open a new script. Alternatively click:
R script
What is RStudio? There are more sophisticated editors compared to R’s built in editor, more broadly, any text editor can support R. Tinn-R and RStudio are popular R editors. This book and relevant examples are indirect products of RStudio. The web page RStudio has instructions on how to download RStudio.