How you can test a hypothesis depends to a huge extent on what your hypothesis is. So we cannot tell you specifically how to test your hypothesis without more information.
More generally, however, here is what you need to do to test a hypothesis. First, you need to ensure that you have held everything but your independent variable constant. You must have your independent variable be the only thing that changes. Then, you observe whether a change in your independent variable brings about the change that you have predicted in your dependent variable. Once you have done this, you will have proven (at least for this experiment) or disproven your hypothesis
Good question. I am assuming that you have done a lot of research and know what has and has not been tested in the past, regarding your particular experiment. One can use that information in order to test a new hypothesis. For example, if one does X, then Y happens. If, in your particular experiment you did something a bit different and Z happened, like you had anticipated or not, then that is a way to test your hypothesis.
Basically, you are doing an experiment to see what you think may happen does actually, indeed, happen.