Each exercise lists the ideal resistance band to use (Tube with Handles or Flat) as well as the muscle groups that are targeted. Many of the exercises can be performed with either band, but be aware that when using the tube band, especially around the feet, there is a chance that it will roll off and could possibly injure you.
Also be sure that whatever you are anchoring the band to is secure so as to avoid any serious injuries that could result from an object falling on top of you.
Using resistance bands can take a few times to get used to, so be patient. After a bit of trial and error you will discover the best ways to use the bands for each exercise so as to best adapt to your body’s specific needs. And believe me, the results you get from these workouts will be well worth a few minutes spent here and there tying knots or bribing a friend (or a kid) to hold the bands in place.
creative, have fun, and get ready to look awesome!