JJBo

Hello, I am new to qigong. I can't find a good teacher in my area so I am exploring online video courses. I started Damo Mitchell's online course on vimeo, for beginners. I am really confused about the basic standing position, more exactly - the knees. Should they be perpendicular to the ground? Like, from the ground to the knees, there is a straight line up? I am looking to learn just from video resources, but I want to have a 100% correct posture.