Depends on your body type. There are 3 types of body types and there are recommendations on what type and how long to train for. Go to bodybuilding.com and find out yours.
The length of your workout depends on how long you want to workout. If you workout longer then you'll need to eat more calories per day. As for losing weight in specific areas, it is impossible to "target" weight loss in certain places. You can't spot reduce. If you want to lose weight, you will lose it from all over your body. You need to adjust your diet, make sure you're getting the right ratio of foods (macros of protein, fat, and carbohydrates) and be consistent working out. It's the long term consistency that's going to make the changes not fad diets or targeted fat loss workouts.
Try http://iifym.com/iifym-calculator/ to help you figure out what you should be eating and how much. Failure only happens when you stop trying. Good luck!