Your essay should follow standard essay format as much as possible. Tell the reader what the question is and what your thesis is. Tell the reader why the question is worth discussing or how you plan to approach the topic. This is where you actually support or prove your thesis. Show the reader why you think so.
Evidence can be a description, a definition, an example or a statistic.
The more evidence you use, the better. However, you do need to be a little careful. Do not show show your reader the evidence. Tell him explicitly how the evidence supports your thesis. Try to anticipate objections a reader might raise to your arguments and deal with them ahead of time.