You may choose simply to state your main point up front before you present the supporting argument. This will help the audience to appreciate the value of what follows, and it will also emphasize that main point. You might reinforce the point by summarizing it after it has been fully developed.

As you develop secondary points, show clearly their connection with the main point that they support. Do not leave it to the audience to figure out. The connection can be shown by repeating key words that express the main thought or by repeating the gist of the main point itself from time to time.