Salt can make your blood vessels and body tissues swell and fill with fluid. This puts an extra strain on your heart. Nutrition labels on food packages will tell you the levels of salt in certain foods, and it will be listed as sodium.
Your doctor will let you know how much is too much. Also, there are a lot of different herbs and spices you can experiment with to flavor your meals, and many restaurants offer low-salt choices. Pre-packaged foods are usually processed with high amounts of sodium. As a good rule of thumb, it's better to buy fresh foods.