Packages in R can contain code, data, and documentation. These are stored in libraries, and provide functionality features to R, like reading .csv files. Packages can be installed with the install.packages() command.
Whenever you use a library that is not native to R, it must be loaded into R by using the library() function.
Excel files can be read with the read_excel() function.
Similarly, data from a .csv file can be stored and accessed like this:
data <- read.csv("/filepath/datafile.csv")
That should show you the rows and columns from the .csv file, which you can then perform operations and analysis on.
More useful functions for working with data files:
readLines() - read text file into character vector
write() - export a dataset as text file
write.csv() & write.table() - export a dataset as .csv file
write.xlsx() - export a dataset as Excel file
save() - save R objects in .RData files