Welcome!!
I agree with Mozzy, use myfitnesspal.com. It's so easy and has thousands and thousands of foods in it. I love it. And nothing touches my lips before it gets logged (so trust me, it's THAT fast and easy!). The app. will also help you set calorie counts to meet your goal. And you can get to the app. on your phone or on your regular computer/laptop, it's really convenient.
I think your goal of 21lbs by Easter is an excellent goal. Just making some simple changes to your diet will help you immensely in the beginning. Once I found out how many calories were in my drinks for the day, that was the first thing I changed! No way I am giving up my calories for a glass of Coke, a glass of grape juice, or an alcoholic drink! My calories are for FOOD only now lol.
I slowly cut out junk food, replacing it with healthier foods. Then I started adding in exercise, seriously only doing 10 minutes a day as I was so wiped out. Slowly I kept adding and now do between 45mins to an hour a day. Don't try to make all of your changes at once as it can be very overwhelming and we don't want that!
The best thing I did was join 3FC. I come here when I am bored and wanting to eat. I read the success stories and mini goals, I join in challenges and read the daily threads. Now, that doesn't mean that I don't eat, it just means that maybe I don't have to stuff my face every single time I get the urge!
I am happy you joined us here, I hope you love it as much as we all do!