Installing R Studio
Go to R Studio and download R Studio Desktop - graphic interface tool for R language.
R Studio is available for multiple platforms: Windows, Mac, Linux.
You can use R Studio for free under AGPL 3. Paid version with more functionality is also available.
Installing extra packages
One of the biggest advantage of R are thousands of libraries which extend R functionality.
You can browse these packages on CRAN repository.
To install new package in R, type:
install.packages("package name")
For example to install ggplot2
plotting library, type:
install.packages("ggplot2")
After installing and before using the package you should load it to the current session:
library("ggplot2")