Congrats on your bow and welcome! Yes, if you are not using feathers, you really need to. If you are using feathers and shooting with a cock feather down, and can not turn or re-nock the arrows (I don't know much about your type of arrows), then I really wouldn't worry too much. The arrow flight should not be effected by this (it will be affected by tune however). Some people actually shoot cock feather in. I'd also get Byron's books and videos, along with Jim Schultz video hitting em like howard. Here are a few links that also might help. Some of the links may suggest anchoring with a field archery anchor, but I'd stick with corner of the mouth.

http://www.centenaryarchers.gil.com.au/the10.htm#Stance

http://www.skookumarchers.com/Archery%20Library/Basic%20Archery%20Shooting%20Technique.htm

http://www.hunting101.com/gunsandbows/bows/bowhunting%20equipment%20and%20skills008.htm