How do you lower the graphics settings on a computer game?

For example, Napoleon Total War. I Want to make the game be able to run on my computer but my graphics aren't good enough. I can't read any of the text or anything in the game. How do I change it from the files rather than the in-game settings?How do you lower the graphics settings on a computer game?
you cant read the text because you didn't set the proper resolution. has nothing to do with your graphic card or chipset. those run the game smoothly, and if the game isn't running smoothly, THEN that means your computer can't handle it and you need to turn it down. I've never played the game, can't tell you, BUT it should all be in the option menu.