What is a good fitness regime for the gym to help with rowing.?

Im just starting at the gym and im 15 years old. I do competitive rowing at school and want to improve my fitness. What would be good to do at the gym to help with this. E.g. core, arms, legs, stomach, endurance.What is a good fitness regime for the gym to help with rowing.?You need to build both strength, and endurance. Ask the instructor to set you a programme of super sets with weights. This is working opposing muscle groups, one set of one then the other without resting between. Then repeat for three sets of each. This will improve both strength, and cardio. for the endurance you need. I got my resting heart rate down by 5, using this method. I have been training with weights, and other methods for many years.