The thesis statement tells the reader what the essay will be about, and what point you, the author, will be making. You know what the essay will be about. That was your topic. Now you must look at your outline or diagram and decide what point you will be making. What do the main ideas and supporting ideas that you listed say about your topic?
Your thesis statement will have two parts.
The first part states the topic.
Building a Model Train Set
The second part states the point of the essay.
has a rich and varied history
takes time and patience
can solve some of our city's most persistent and pressing problems
Or in the second part you could simply list the three main ideas you will discuss.
has a long history, blends traditions from several other cultures, and provides a rich heritage.
requires an investment in time, patience, and materials.
helps with traffic congestion, resource management, and the city budget.
Once you have formulated a thesis statement that fits this pattern and with which you are comfortable, you are ready to continue.