If this is your first time to use dumbbells and have no injuries I would suggest you use lighter weights 3-5lb and then as you progress and feel more comfortable working with dumbbells you can work your way up. You do not want to start with a 10lb weight if you have not used weights before as this can lead to injury.
Hope you enjoy this Pace and Go Program. They have an Intermediate 8 week program that you may be interested in after you finish the 21 day Athlete. Enjoy!