so I can see changes in sales by month on a year to year basis. for example 2014 might be the blue bar above each month, 2015 red, etc
Display in the same chart as many series as the required number of years and give a different color to each year.
Basically, the procedure is identical in Draw and Calc but Draw is far less versatile and capable than Calc. Moreover, I suppose you already have your data in a spreadsheet. Consequently, I suggest you design your chart directly with Calc, avoiding the error-prone retyping. The resulting figure can be inserted (pasted as a picture or linked as an object) in a Writer document or any other.
If this answer helped you, please accept it by clicking the check mark to the left and, karma permitting, upvote it. If this is what you expected, close the question, that will help other people with the same question.
thanks for your reply. could you elaborate on the step by step process for someone who is ignorant on Charts 
Yes, I have all the data loaded into the spreadsheet. thanks!
You can get a lot of the step by step procedures in the documentation. See Chapter 3 - Using Charts & Graphs. For LO documentation click here.
You may have a look on the screenshot (OpenOffice)…
The data are positioned in 3 colums for each year. It’s only a simple example.
Start the chart wizard and then move the data series as you like it (see cursor an that position). The data should be in the same sheet…