Technical question about hand and forearm during freestyle

Looking for some technical assistance here. When starting the catch/early vertical and I am keeping my elbow high and holding water should i think of leading with the hand or the forearm? I've read that you want the hand slightly ahead (closer to feet) of the elbow so that makes me think you have to lead with the hand. Thoughts? If you had an image of a string pulling your forearm or your hand (toward feet) where would you place it---hand or forearm? thanks for your help