Welcome to 3FC =)
Make sustainable changes. Things you know you'll be able to do. For example: If you've never run a step in your life, then don't expect to be running an hour a day 6 days a week to start. Start by walking, and then when walking feels good and becomes a habit, then build it up a little bit at a time.
Start being mindful of what you eat. There are a million methods to do this, but try writing down what you eat for a week. Even if you don't change anything, you might be surprised at what and how much is going into your body. Aim for more fruits and vegetables with each meal. Aim for more water, and fewer drinks that contain lots of calories.
Look around, maintain healthy changes, and then add in more and more changes as time goes on.
You can do this!