Well with sqli all you need to do is find one injection point for sqlmap to use, try finding a file with a .php extension and a parameter like .php?X=<something> next you will need to see if you can cause an error in that by sending a wrong input like .php?X=1' which usually will cause an error that is displayed on the page that is visible. If that works then you can put that entire link into sqlmap but not with false statement but with the actuall page that doesnt cause an error because sqlmap will add everything it needs in the --wizard. I personally prefer doing the injection manually in the browser instead of using sqlmap unless i dont have time, its a pretty basic concept and all you need to know is how to cause an error and how to craft sql statements.