Welcome to the forums.
This is a great place to get help and support. But ultimately the job comes down to you about how you do it.
I know exactly how bad it feels, i was 317 and im now -100lb, and the feeling now is fantastic in comparison!
So sort out HOW you are going to do it. Calorie counting appears to be the most popular and effective tool. You can sign up at fitday.com or sparkpeople.org to log all the food you eat so you can keep track of it.
Sign yourself up a diary in the diaries thread so we can all support you as well, and have a look and comment on other peoples diaries.
Best wishes!