Wow. 100 lbs is a lot, dood. just dun be discouraged when u get see results fast. it's gonna take a while before u reach ur goal. as for the workouts, you should do both cardio and weight lifting.
For cardio, as long as you do moderately intensive exercise, such as running, biking, rowing, etc, between 25 - 45 minutes, 4-5 times a week, you're good to go. However, you may need to build your body up to it. And trust me, it takes more than just a few days.
Now weightlifting, you need to do some researching of your own, cuz there's just too many idfferent exercises. All I can tell you is that you need to lift for around 45 min per session, 3 times a week.
That should get you started, man. It's a long way ahead of you, pal. Let me know how it goes.