If you don't have any experience with running, are overweight and a poor fitness, I always recommend the Couch to 5K (C25K) program. Which consist of 3 to 4 workouts per week that last anywhere between 20-30 minutes of moderate exercise.
The reasons for this are:
- it assumes you have no running experience, so it takes the time to built up strength in your legs, so you shouldn't get injured
- it alternates between walking and jogging, as opposed to other programs that alternate between jogging and running. The walking intervals means you get plenty of rest and don't strain yourself. This also helps prevent overuse injuries.
- it starts out with very short, low intensity workouts, which again means you won't get injured, you shouldn't have a lot of DOMS and you should be able to complete each workout. That last part is important, because when done correctly anyone should be able to to finish C25K, which goes a long way for motivating people!
An important factor is that you should never run too fast. With which I mean you should
be able to hold up a conversation while jogging, else its too fast. Yes, this almost certainly means some abysmally slow pace, but given that you were completely sedentary before you started, its a huge progress! Basically, you're not working out to lose pounds right now, you're working out to get into great shape, so you can lose pounds after the program.
The most important thing to focus on right now, is no excuses and getting started, keep it up and when you're done with C25K, pick a new target. Whatever you do, don't stop working out!
As for your diet, I believe that should be a different question, though the easiest way to track your calories is keeping a diary and spent some time figuring out how much calories are in everything you eat. Assuming your overweight because you eat too much and haven't worked out, cut out any candy and alcohol from your diet right now. You don't need the stuff and they will only make you fat.