R does not come with a builtin editor.
If you don't have a preferred general use editor (VisualStudio, emacs, vim), you should install Rstudio in addition to R
Instructions for installing R and R studio are described below.

R

Windows

1. go here
   https://cran.r-project.org/bin/windows/base/
   
2. Download latest version by clicking on link, for example: "Download R 4.1.1 for Windows"
   
3. install exe file once downloaded by opening the exe file
   

MacOS

Method 1

1. go here
   https://cran.r-project.org/bin/macosx/
   
2. Download latest pkg version by clicking on link, for example: "R-4.1.1.pkg"
   
3. install pkg once downloaded by opening the downloaded pkg file
   

Method 2 - via brew

1. open terminal
   
2. check to see if the brew package manager is installed by running the terminal command
   brew -v
   • if you get an error, or no output, run
     /bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"
     
3. Intall R via brew by running
   brew install R

Linux

Follow instructions here for debian, fedora, redhat, suse, ubuntu distros
https://cran.r-project.org/bin/linux/

For Arch based distros
sudo pacman -S r

Rstudio

Windows/Mac/Linux

Download the appropriate installer from:
https://www.rstudio.com/products/rstudio/download/#download

Mac method 2 - via brew

if you followed Method 2 above for R's base installation
brew install –cask rstudio