Naomi Folkard explains how to get the right head position for beginners.
Archery is a repetitive sport, therefore the simpler your technique, the easier it is to repeat. Complicated movement patterns in the body and head can create tension which makes executing a good shot difficult as well as making consistent repetition difficult.
Ensuring that you keep the legs, torso (apart from a rotation into alignment) and head still leaves you with just the arms and shoulders as the only predominant moving parts to the shot, this will give you more control and understanding of your shot.
Taking this fundamental point while focussing on the head specifically, the head needs to be set in its full draw position at the beginning of the shot. Many archers like to look at the placement of their fingers on the string to help ensure that the fingers are placed in the correct position every arrow, this is fine so long as the posture and head position are set immediately after, and before you start the draw.
It's really important that the neck is relaxed throughout the shot, not only because a tense neck is really uncomfortable and may lead to pain when not shooting, but also because the tension can spread into the shoulders and make expansion and a good shot execution difficult.
If you are finding it difficult to be relaxed then try a lighter bow or rubber bands until you can switch off the neck muscles while completing the shot.
The position of the head should be towards the target but not perfectly square on as this can introduce tension, you should be able to see the target just to the side and slightly above the nose. You can use the picture of your nose and target to help you ensure that your head stays still during the shot.
Thinking about the other dimensions for the head position may be too complicated for a beginner, but it will vary slightly upon your head shape, jaw line and nose and where you want the anchor to be. As a guide it's normal for the string to be comfortably on the front of the chin and nose (without squashing it) at full draw, while expanding. The string hand should fit lightly under the jaw.
You may find that you need to tip your head a little to the left to do this, remember to make this tip at the beginning of the shot. If you have a side anchor this tip won't be necessary.
The key is to find a comfortable head position which is easy to repeat and it should keep still throughout the whole shot. Some experimentation with a light bow is expected. If you are very new to archery it may be necessary to return to the subject on numerous occasions over a few months. It can be complicated for the less coordinated and it is okay if your learning and discovery process takes some time, be patient and enjoy the journey.