At this point, you should be able to load the R packages you need for this book, and you can do so using the library() or require() functions, both of which take the name of the package you want to load as an argument.
You may be wondering why you need to load packages into R to use them. If every package were loaded into R by default, you may think you were using one function but really be using another. Even worse, it's possible for there to be internal conflicts: two different packages may use the exact same functions names, resulting in strange and unexpected results. By only loading packages that you need, you can minimize the chance of these conflicts.
