General Help

# provides general help links
help.start()   

# searches the help system for documentation matching a given character string
help.search("linear regression") 

Help & Examples

help(mean)      # provides details for specific function 
?mean           # provides same information as help(functionname) 
example(mean)   # provides examples for said function

Installing Packages

# install package from CRAN
install.packages("ggplot2")