I need help to write my thesis on Animal Farm; please help me start.

In order to write a good thesis on Animal Farm or any other literature, you need to know what makes a thesis a good one. 

First, a good thesis is always debatable. If the thesis is not debatable, it cannot be a good thesis. For example, the statement that Napoleon is in control, is not not a good thesis statement, because this is obviously true (and so not debatable).  However, the statement that the animals are better off under Napoleon, because they think they are happier, is a good thesis statement, because not all will agree with you. 

Second, a good thesis statement is also cogent.  In other words, you have to be able to prove your thesis statement from the text. If you do not have evidence to back up your thesis, the thesis is weak, and it should be discarded. You should have a few key supporting point that you can elaborate on, along with quotes.