Ken's course and the Student's areas of the forums have extensive information on support. Support is crucial to great singing of all kinds. Theatrical singing is included in the great need for super support.
Support is how you regulate and control the breath that you sing upon.
You can watch a number of Ken's YouTube Videos for beginning singers and he gives some basic explanations of support.
Here are a few to get you started. Keep watching as many as you can. Then take Ken's course and get the benefits that can come from a full course on the voice.