Do the first round with light weights, weights that your certain you can do. You could even do the lower body exercises with just your bodyweight when your getting started. If after this first round the weight is way too light and you know you can go much heavier, just consider it a warmup round and dont count it. Ideally, you want to use weights during your “working sets” that are challenging but not necessarily taking you to complete failure. If a set calls for 10 reps and you could complete 17-20 plus reps with that weight, its too light. If your failing at 10 or less reps, then you need to lighten the weight. You want the last few reps of each set to be pretty challenging. Strive to find a weight for each exercise that you would only have a few reps left in “the tank” for. As your body adapts throughout the program, youll get stronger and be able to add more weight during the exercises. Keep in mind that your form is most important, never compromise your form just to add more weight to an exercise. Trust the process, your strength will come!