As a general rule of thumb, most adult beagles need around 1-1.5 cups of dry food per day, divided into two meals. Puppies need more food than adult dogs, so they may need up to 3 meals per day.
If you're unsure how much food to give your beagle, you can always consult with your veterinarian.
In addition to food, beagles also need access to fresh water at all times.