Add the sugar into a medium/large mixing bowl. Add very warm water - it should be pleasantly warm to the touch (it's best to check its temperature with a thermometer, it should be 100-110°F (38-43°C)). The water can't be too hot or the yeast won't work. Stir the water with sugar.
Stir in the yeast. Let stand for 5 minutes until foamy (a sign that the yeast is working).
Add all the other ingredients for the dough: flour, melted and slightly cooled butter, and salt (note about the flour: if you're using measuring cups to measure out the flour, add 3 cups of flour first and then add the remaining 1/2 cup while kneading the dough if it's still sticky, if using a scale you can add all the ingredients as written in one go).
Stir the dough with a spoon until roughly combined.
Knead the dough by hand or with a stand mixer fitted with a dough hook attachment - about 3-4 minutes until the dough is smooth and not sticky.
Cover the bowl with a kitchen towel and let stand in a warm place until roughly doubled in volume. You can put it in a turned off oven with a light on. It should take about 30-45 minutes.