Hello. You will normally find instructions for how long to cook the chicken on the label if it is from a supermarket. A medium sized one normally takes me about 90mins on 180c (Gas mark 6ish). You can do your potatoes how you like. I tend to cook them for about 15 mins (start peeling when the chicken goes in the oven), then toss them with some olive oil and crushed garlic. Then put them in the oven with the meat. If you want to go simple, you can just chuck them in the oven with the chicken without the boiling etc but they will not be so crispy. Good luck, it's making me hungry!