Debian

Installing R on a debian-based system is generally just a matter of

apt-get install r-base

However, to get access to the latest verion of R (and packages) using apt-get, one needs to add a new software repository to /etc/apt/sources.list.d, update the available source lists and proceed with installation.

See for example here, here or here to get instructions on how to add such a new repository and the DEBIAN PACKAGES OF R SOFTWARE page for the URL of the repo and all the details about the debian R packages.