You can download and install R for Linux, windows or Mac from here. Select the platform that best describes your system and install R.
In Linux, R can be started from the command line or terminal by just typing "R" and pressing enter.Once the R language is started, we are free to use the R language commands to perform various functions. You can come out of R by typing "q()" and pressing enter.
Most R installs come with a html help manual which opens in the default browser and can be started by typing "help.start()" and pressing enter.You can even look here if your httpd server is running.