You can use resistance tubes the same way you use free weights. The key is to work each muscle group frequently enough so that it grows, yet not too often so you don't over-train and cause injury. More is not better and here is why...
As you work your muscles against resistance, the muscles develop microscopic tears in the muscle tissue. You must rest the muscles enough after each workout so that the muscle fibers can repair completely. when the muscles heal, they create a stronger and larger muscle.
Here is a body building program from a former Mr. America and Mr. Universe. It works each muscle group three times over a two week period. Each day you'll perform one of the three workouts, or get the day off.
Rep Range: 8 to 12
Sets: 3 sets per exercise
Time Between Sets: 45 seconds to one minute
Workout 1:
Chest: resisted pushup, one arm chest fly
Triceps: kneeling triceps extension, two arm triceps kickback
Biceps: standing biceps curl, one arm preacher curl
Workout 2:
Back: overhead back pull, seated back row, good mornings
Shoulders: front shoulder raise, standing lateral raise, shrugs, seated rear shoulder pull
Abs: resisted crunch, standing ab twist
Workout 3:
Legs: squats, lunges, laying hamstrings curl, standing calf raises
Week 1
Mon: Workout 1
Tue: Workout 2
Wed: Workout 3
Thu: Rest
Fri: Workout 1
Sat: Workout 2
Sun: Off
Week 2
Mon: Workout 3
Tue: Off
Wed: Workout 1
Thu: Workout 2
Fri: Workout 3
Sat: Off
Sun: Off