You need to restrict your intake of fat, particularly saturated fats .
Red meat, pastries, cakes, biscuits, hard cheese, butter, fried foods and so on need to be severely restricted for now.
Eggs, liver and prawns are high in cholesterol, but have lots of other health benefits so can be eaten unless you have been told not to. Moderation with these foodstuffs.
Fibre can help lower cholesterol - so plenty of fruit, veg, beans, oats and bran type cereals.
General exercise is important - so treadmill and other cardio machines will be good and strengthening exercises with weights will do no harm. But the most important thing is to enjoy the exercise you do do. A good walk in the fresh air or a kick about with a ball will be just as beneficial. Swimming too.
Unless the doctor has prescribed tablets, then they are best avoided.