The folder that you work through the terminal is known as the working directory. To know what your current working directory is, use:
> getwd()
which will return the path to where you are. To specify a working directory, you need to put the path to that directory in, which is shown in the example below.
> setwd("/Users/Path/Through/The/Computer")
Similarly, if a directory called Land within Computer needed to be accessed, then use:
> setwd("Land")
to access it.