I have been weight training and it is very effective for weightloss in my experience. I do some of everything, slowly increasing the weight that I use, and I have a personal trainer who gives me a new programme every 4 months or so so I switch it up. It builds muscle, which increases your "fat burning engine" essentially. So when you're sitting around not working out, you're burning more the more muscle you have.
I cant get my exact stats right now because they are on my other computer whose battery and power cord have died, but in the first month or so that I started seriously doing weights I took at least an inch and a half off my waist. It also helped break my plateau i think. So in my opinion it is great for weight loss. And it makes the gym more fun
If you arent sure what to do, ask at your gym to get someone to show you, they should be happy to. My gym does a "gym explorer" that goes around, showing you how to use the weight machines and gives you a workout at the same time. Or if that doesnt appeal many gyms have weights classes which are fun, and you can learn a lot about technique and eventually apply that to the machines on your own when you feel comfortable. Just dont be afraid to ask for help! Theres no sense in injuring yourself because you were embarassed to check