The web is your friend as you learn to use R. The R user community is large, friendly, and usually very helpful*. We often have a search engine window open as we work in R to look up new functions and packages or to figure out what error messages mean.
* Do take time to read the posting guidelines before posting to the R help forums though - providing the community with enough information for them to help you is important!
Installing R - Go to http://cran.r-project.org/ and download the
appropriate file (or if you are using a major Linux distribution, you
can install from the repositories).
RStudio (Gui for R) - Provides easy to use platform for using R. We're sold on it - it makes using R way easier! (https://www.rstudio.com/)
Rseek.org - a google powered search engine for R. Makes finding help
easier.
Statistics: An Introduction using R. Michael J Crawley. 2005. John
Wiley and Sons. Good basic intro, we often refer to this.
Simple R: An introductory textbook in pdf format. http://cran.r-project.org/doc/contrib/Verzani-SimpleR.pdf