STS is a great series...but if you haven't lifted...and don't have a base of weight lifting...I personally would start with Cathe's total body weight workouts first...such as STS Total Body, Muscle Endurance, Hi Reps, or Muscle Max...to work the WHOLE body 3x per week to give a good strong muscle base.
I have been out due to injury for 4 wks...and as soon as I am released to get back into weights...these whole body weight workouts is where I will start because I will need to work on the whole bod after being off,,.. and these are so concise, thorough, and effective. After doing those for awhile, I will then tackle my STS again.
best wishes...and whatever you choose to do...just be sure to lift...it is soo good for the female body!