The original data file is located here: https://data.cityofchicago.org/Environment-Sustainable-Development/Energy-Usage-2010/8yq3-m6wp
Click on the Export button to convert it into a CSV file.
I did not make any changes to the data file outside of R, and you certainly do not have to do that either. However, this is a pretty large data file so it might be best to remove a couple of columns before you load it in. You really do not need to make any significant changes to the file inside of RStudio either. I added another column to copy the census block over so it is easier to merge the data with the block data for Chicago.
This is what the spreadsheet should look like:
The original Excel file
What the link above should lead you to, you click on the Export button (the third button from the left) and then click "CSV" to convert it to a CSV file.