Hi sharlie,
You and/or your health care professional(s) will know the blood-sugar range that you are aiming for. Your meter shows what your blood-sugar level actually is.
Simply, the idea is to stick to the foods which keep you closer to your target range, and try to avoid those foods that take you further away from it.
At first this requires a bit of time and effort.
The first phase of "Eat to your meter" means taking time to test your levels before eating, note what (and how much) you eat, and then test your levels in the hours after eating. If you can put some time into this task for a couple of weeks, you will soon get an idea of the foods that your body tolerates and does not tolerate, with regard to your blood-sugar level. This knowledge soon builds up and pretty soon you get to know the foods that will and will not cause problems for you.
Regards
Antony