Contrary to popular belief your core consists of more than just your abs and does more than just look good on a beach.
A solid core is key in helping you with most exercises and movements you will do both inside and outside of your workout.
So focusing on the core is key because all movements start from a strong core.
Again we're going to go through a few classic core exercises modified to use the resistance band: Crunches, Cable chop and the Pallof Press
Again treat the core like you would your other muscle groups and aim to complete each exercise for 8-12 repetitions, 3-4 times over but again feel free to scale this up or down depending on ability.
We would recommend The Green GoodBand for these set of exercise