R is typically used for statistical computing, you don't necessarily need it to just merge some CSV files. Do you know python for example? The standard library provides functionality for handling csv files. Or indeed you could use Pandas (which has some similarities with R).
There are beginner guides available on the official website, if you're familiar with Matlab or NumPy then similar principles apply - the language itself is slow but the underlying functionality you make use of is in C, fortran etc.. and rather fast so you'll often want to avoid loops where you can and instead vectorise your code.