If you are not already an R user, you will need to install R on your computer. To do so, visit the R Project web-page www.r-project.org and follow the installation instructions that you will find there in the "Geting Started" box. The whole process should take only a few clicks. There are versions available for Linux, Mac and Windows. The way we use R in a Windows environment is to create a folder for each project, with various sub-folders including one from which we run R and in which we store sequences of R commands as plain text files (R scripts), and one in which we store data-sets, usually as plain text files but sometimes in other formats that R can read. Experienced users will doubtless prefer other, more sophisticated ways of keeping track of their work, but your minimal goal should be to maintain records that enable you to reproduce your work at a later date should you need to do so.