The easiest way to carry a theme through a presentation is to decide what the presentation is going to be about and then go back and figure out what theme fits the goal you are trying to reach.
Once you have figured that out, take that theme, look at each of your main points, and see how you can wordsmith them to tie in better to your theme.
For instance, let’s say the convention theme is “Light Their Fire” and your presentation is on sales. You might say your theme title is, “Lighting up your sales force.” Your first main point might be, “How do you start a fire without any matches?” Your second main point may be, “How to keep the fire burning?” Your third point might be, “What to do when all you get is smoke?”
Try not to be too cute with themes, for you will lose some credibility with an analytical audience.