The glycemic indes refers to how qickly a food is turned into sugar and enters your blood stream. High index foods are faster and will cause a spike in blood sugar. Low index foods are released more slowly and keep your blood sugar steadier. Usually low index foods are less processed and lower in refined sugar.
Some nutrition experts believe the glycemic index is the best way to control blood sugar. There are several problems though. First of all, there are hundreds of foods and it is impossible to know the glycemic index of them all. You can look anything up on a table but nobody is going to do that before they eat all the time. Secondly, is the concern the glycemic index of each individual food, of the total meal or of the total day? It is just to hard to apply to daily life. That is why most diabetics are taught to count carbohydrates with an emphasis on high fiber, low processed foods. It ends up controlling the glycemic index somewhat but it is easier to follow.
You probably will probably do well if you eat about 60-75 grams of carbohydrate per meal or at least keep the amount of carbohydratet you eat consistent throughout the day. Did you have an opportunity to see a registered dietitian about your diet? If not, I suggest you do so. It should really help.