I would love to give you some helpful advice on this matter.
A busy schedule is the #1 reason why fast food is so popular, but you cannot exchange your health for convenience. I am glad you want to make a change, that is step one.
Now these are the steps to making it happen.
1. Stock your kitchen with healthy foods that are quick to grab on the go. examples: apple, banana, orange, baby carrots, nuts, yogurt cups, rice cakes, power bar etc
2. throw away any processed or unhealthy foods in your house. If you are trying to avoid eating unhealthy, get it out of the house
3. ALWAYS pack a snack bag AND a lunch, full of non-processed healthy foods to take to work
4. don't allow yourself to reach starving point because once you reach this point you will go straight for the fast food. Keep a power bar or some kind of snack on hand at all times to prevent unhealthy eating
5. get a routine! schedule a good time to grocery shop every week and stock up with all the "quick foods" and meal items you will need for that week.
6. If you do get too busy to pack lunch research all the healthy places to eat close by your work. There is ALWAYS an alternative to fast food that is easy and delicious and HEALTHY
7. You are a go-getter, you can do this!