You are not alone, everyone has to start somewhere. There are people that work in that area that are required to teach you how to use all of the machines properly. Don't be afraid to ask all of your questions and also what their favorite machines are. The best machines to use are the ones you enjoy or hate the least. I really enjoy the hand bicycle, the rowing machine and the bike. I like using the treadmill also but for now I can not use it because of my ankle.
Read this article for a small introduction to the Cardio Machines you will find in your gym and tips on how to use them. You will feel a little less alienated the next time you walk into the gym.
Also when you go to work out, make sure you are wearing comfortable clothing that is not going to get caught on anything or fall down. And bring a MP3 player, iPod, iPod touch with some fast upbeat music with you. When you workout focus on the music and forget everything else in the room it can make a real difference between a 15 minute workout and a 60 minute workout. (Do not bring your cell phone, no one wants to hear your one sided, very loud, conversation)
Funny Story: Last semester I was so focused on the music that I didnt realize the whole school gym had emptied because of a fire alarm going off. Now to be fair there weren't that many people in the gym and there was not one of those flashing red lights. Someone should have come up to me, one of the teachers or aids though, don't you think?