Do yourself a favor.
Get yourself a copy of
Starting Strength. I got mine on my Kindle, and read it cover to cover twice before I entered the weight room. I was inspired by a friend of mine who was 315 or 325 last year. He just hit 220, and is starting to resemble some kind of balding Viking.
This is NOT EVERYTHING you will EVER need in a weightlifting guide. What it does is lay a SOLID foundation for everything you do that comes afterwords. It is intended for the weightlifting novice. He explains the big 5 main barbell exercises, how to do them correctly, how your body should look as you perform each one, at each stage.
I'm still only a couple weeks in, and I'm starting to see/feel the difference. I have done 4 of the 5 exercises so far. I can tell you now that I'm still not certain I could bench my bodyweight, but I don't care at this point. Because each workout, I add another 5, 10, or 20 pounds onto my exercises, and my gains keep increasing. And if they don't increase, that's reassuring, because that means I've gotten out of the complete newbie phase, and the fun stuff can begin.
You have it in you to do great things, and being bigger, you actually have it easier with regards to weight-lifting: your body has already shown it can store the energy it will need. Now all you need to do is make your body work.
Don't worry about how you look in the weight room. Study the exercises. Don't rush yourself. It doesn't matter if the guy who came before you slapped 3 45s on each side of the bar before he hit the rack, and made it look easy. It doesn't matter if the woman next to you does more squats with a heavier weight, while you're struggling with a couple of dimes on the bar.
What matters is that you keep trying, and keep doing the exercise RIGHT. The gains will come. The fat will melt, if you're working hard. Your body WILL adapt, you WILL increase your gains, and in the span of a few WEEKS you will see drastic improvements.
Just imagine what you'll see after a year.