Welcome to 3FC =)
The start is always the most daunting. So many things to think about, and it seems a little overwhelming.
Start at the beginning.

1 Step at a time. You don't need to change everything in a day.
For example... what do you tend to drink when you're thirsty? Sodas or other high calorie drinks? You could always choose for a week to focus on getting in more water.
How many fruits and vegetables do you eat in a day? At least 5 servings with most of them being vegetables? If not, try adding more in one meal at a time.
Do you know how many calories you're taking in on a normal day/week? Try counting up all the calories that you're eating -- not even changing anything (yet), but counting them up to see just how many you're consuming normally.
From any of those points you can start. You can begin to see a couple patterns, and you can get a better idea of what you'll need to change.
We'd love to help and support you along the way.
Hope to see you around the boards!