This is how the chuck works in a bowl making scenario.
You take your bowl blank, lets say a 6inch round by 2 inch deep, and affix centrally to your not yet acquired faceplate, using screws.
The face plate is fixed to the inside of the bowl which you will hollow out later therefore removing the screw holes.
Shape the outside edge of the bowl.
on the base (foot) of the bowl you will create a recess, slightly dovetailed, into which the jaws of the chuck will expand into.
There is an optimum size and shape for the recess hopefully indicated in the instructions, but essentially giving the chuck as much metal to wood contact as possible.*
finish shaping and sanding your outside of the bowl.
remove the face plate from the lathe and bowl and affix chuck to lathe and then bowl to chuck, spinning lathe by hand to check centrality. Once you are happy with the fitting you can proceed to hollow your bowl etc.
*The chuck jaws should form a proper circle when open X amount, this would be the optimum size for your recess. too large or small a recess will result in the chuck only gripping by its edges/ ends and would not give you much support or grip.
see attached very rough sketch