I will give you the simplest advice that worked for me. Find a friendly or what seems to you an interested face and speak directly to that person. Someone towards the center or back of the room so it will seem that you are looking out to the crowd.
If you are inexperienced and you start allowing your eyes to wander you might lose your train of thought or stumble. So find a face and speak as if you are speaking to a parent or a spouse. You will have no problem and no one will know that you are not addressing the entire room.
Don’t think about how you are going to be received, they are not there to judge you. They are there to hear the information you want to share with them. And you are there to share information with them. They don’t care if you have a hair sticking up out of place, or you forgot to button your top button, and they won’t see the spot on your tie that you didn’t notice till the last minute. Or if you are female the run in your stocking. If you have a message you want known, then know you have something important to share, just as if you were sitting in your living room or walked in on a group of your mothers friends and stated your opinion. YOUR opinion counts and you have a right to voice it. So it is important for you to speak your opinion and let others know what is on your mind. Sometimes you are going to be the one sitting and listening and sometimes there is going to be a lucky listener hearing what YOU have to say.