First create a new project in RStudio and put your csv files in the project directory. Then create a new R Script to work in.
In R you typically want to get your data into a dataframe where each column is a different kind of data. For rectangular data like yours, you can do this using gather from the tidyr package. Try this:
library(readr)
library(tidyr)
# read in the data
sales <- read_csv("Sale_Counts_State.csv")
value <- read_csv("State_MedianValuePerSqft_AllHomes.csv")
# gather
sales <- sales %>%
gather(key="month", value="sales_counts", starts_with("200"))
value <- value %>%
gather(key="month", value="median_value", starts_with("200"))
You might need to install the readr and tidyr packages. This can be done with
install.packages("tidyverse")