You need to really understand division first. One of the problems I see many people have with math is that they do well at first, but later get to a concept they may not understand well, but just sort of sweep it under the rug as class moves on to the next topic. That may be okay for something like history or English, but in math, almost everything builds on earlier concepts, so you can get really behind and not understand things. Never let anything slip if you don't understand it. Put in the extra time to really understand everything. You will not only get better grades on a test, but future math topics will be much easier.
In any case, I think these videos will help you get a better understanding of division. Keep watching them until you get it and pause or go back if you don't understand something 100%. Don't move on to the next video until you master the one before it and practice, practice, practice.
Here is a good starting point on Khan Academy for more help. You may need to start at the complete beginning, since part of your problem may be issues with basic addition/subtraction/multiplication which you must really master before you can do things like long division.