Your questions do not indicate whether you have accumulated any information about the Boston Tea Party and whether you mean "start" the writing or "start" doing the research. I used to write a lot of research papers without knowing much if anything about the subject. I found that the best way to start doing the research was to refer to an article in an encyclopedia or other reference book. eNotes has a fairly long article about the Boston Tea Party which you can access by clicking on the reference link below. It also provides a number of bibliographical sources. You should read an article like this and pick out the salient facts, then do more research on those facts. You don't want to make a life's work out of this project, and your teacher isn't expecting you to contribute anything new to an event that has been studied and written about for over two hundred years. The amount of research you do should be determined by the number of words you are expected to write. Basically I assume you will be going over the principal events which are covered in articles in such sources as the Encyclopedia Britannica and the Encyclopedia Americana. Articles such as these ought to give you a framework to follow and some solid bibliographical sources. Also, be sure to read the eNotes article referenced below. LOL.

It would be interesting to include the fact that many of the 'Mohawks' (your destructive 'terrorist' cell) were prominent community members and business men.  They dress up like Native Americans, but many witnessed the event, and those disguises were fooling no one. 

An interesting way to begin the introduction of the Boston Tea Party might be to retell briefly the events of the night, including really interesting details or motivations of the colonists, but without giving away that you are talking about something historical-- you could make it seem like the event happened recently.  Then go on to discuss how we would label the events or perpetrators; I am pretty sure that we would have labeled them terrorists!  However, back in the day, these men were seen as revolutionaries fighting for a cause by the colonists.  Then you could launch into the specifics of your paper and your thesis statement.