There are 1440 minutes in a day. Start devoting 10 minutes a day to physical activity. When you find out where your downtime spots are in your day, add another 10 minutes. This can be an easy 1st step into getting into the habit.
Just think- if you devote 40 minutes of time for yourself, you're still left over with 1400 minutes to do the things that life throws at you. You have the time, even in a busy day.