Engaging with your audience when presenting can be a difficult skill and using eye contact is the key to gaining their attention. When presenting PowerPoint slides you may be tempted to look back at the screen behind you, but if you do that you will lose contact with the audience and it will lower their engagement.
To avoid problems, first make sure that your presentation PC is setup correctly before the presentation so that you can trust that the display behind you is working once you start speaking.
When making eye contact it is also important to scan across the audience to people in each part of the room. A friendly face can be easier to make eye contact with, so part of your skill needs to be to make contact and engage those that are not already warmed up to your presentation.
Another important part of the skill of making eye contact to create eye contact with individuals, and not just “look out” at the audience as a group. Keeping moving eye contact from individual to individual as you cover the points in your presentation will keep them interested and engaged.