How do I focus the lenses?

The lenses are standard M12 security-camera type lenses. They thread into an aluminum block inside the hand frame. Either reach in there with fingers and spin the lenses, or (very carefully!) use very small needlenose pliers to grab the outside of the lens head and spin it to where you'd like it.

The lenses were focused before shipping, but during shipping they likely walked around a bit. Since some users will want focus at infinity, and some users will want a closer-range focus, we didn't use loctite on the lens threads. However, when the lenses have been located as desired, you'll most likely want to apply a tiny drop of superglue or loctite on the top of the threads using a long needle-type applicator, to prevent it from vibrating loose during operation. Just be very careful not to get any adhesive on the face of the lens, or to use so much adhesive that the bond can't be broken later to re-adjust the focus.