How do I make a bar graph
What have you tried so far? See my suggested guidelines for asking, especially the first and second points.
I believe the best way for you to do this is by following the step by step instructions in the documentation. You can find the LO docs on this page. Refer to Chapter 3 - Using Charts and Graphs for details. Note: v4 docs still apply for most part regardless of version you are using. Main difference may be in location of some menu locations as menus changed around v5.3. Also you may want to look at Getting Started guides toward the top of the same post.
Since you have not given a specific indication of your need, conditional formatting Data Bar may be an answer to your question.
Interesting; I had no idea that feature existed. I would +1 except without more details from the questioner, I do not know whether it answers the question.