Congrats on the membership.
Most gyms have trainers walking the floor who will show you how to use all the equipment for free. Don't be shy about asking one of them for help -- it's best you learn proper form now than to train with risk of injury or train ineffectively because of poor form. Plus, everyone starts out at square one at some point, so ask all the questions you can think of.
Second, concentrate on training your whole body in whatever sort of split is comfortable for you -- muscle is your furnace, remember. Combine that with a clean diet and some cardio and you'll see improvement in your stomach. Fat loss just math -- create a deficit. This is 90% diet, but it's expedited by cardio -- not to mention the heart benefits of cardio. You will reduce fat all over via this method, but you can't pick where you lose fat from. But be patient, it will come.
Bars -- glorified candy bars. I'd suggest not making regular use of them. I don't even like them as treats personally. Usually just cheap quality whey and soy concentrate mixed with some high-GI carbs. Sugar free? Sure. But they'll cause insulin spikes just as severe as refined sugar will, in some cases worse.
Shakes -- depends on the shake, it's a mixed bag. Pre-mixed (bottled/canned) MRPs often contain a lot of sugar and miscellaneous additives. Buying the powder is best. If you make your own, they generally aren't bad as supplements, and are in fact advantageous after training, but don't let them replace whole food sources at meal times.
Also keep in mind that (with the exception being the beginner stage for anyone, or for a little bit longer with highly overweight folks) building muscle while losing bodyfat is not terribly achievable. It's a cyclical process. To build muscle, you will need to gain some fat as well; however, it's quite possible to keep the proportion of fat gain low with a clean diet. Likewise, to cut bodyfat, you will inevitably sacrifice a bit of muscle. This can also be minimized, but it's a long story.
Anyhow, concentrate on whichever is more important to you at this point and evaluate your progress down the road. When doing one, it's quite possible to see small gains in the other, just don't expect to see dramatic gains in both at once. That requires a cycle.