Organizing your speech according to topical organization means you organized your speech:

Organizing your speech according to topical organization means you organized your speech: based on categories of information.

Explanation:

Categorical or topical organization is the most common one for organizing speeches. This type of organization consists in dividing the message into categories or chunks of information. These chunks are connected and function as support for the main message.

Suppose you're giving a a speech with the purpose of convincing people to quit smoking. Your general purpose is to persuade. Your specific purpose statement could be something like "I will persuade the audience that smoking is unhealthy." The categories inside your main point could be:

1. number of deaths associated to smoking;

2. types of diseases associated to smoking;

3. testimonies of people who quit smoking and are healthier now.