Will you sort out my workout plan at the gym?

I need to lose a stone and a half by august. My diet is fine - I'm following weight watchers so am eating under 1500 cals a day. I want to lose fat, not turn my fat into muscle and can only go to the gym 4 times a week - tues, wed, fri and sat. I have an aerobics cl on saturday so that's sorted. I really don't want to use the equipment for over an hour each day. My gym has bikes, treadmills, steppers, a rower, cross trainers and weights. Please help me as I don't know what to do...the fitness instructor at the gym is no help.