Sample Books-Render image in iOS

Hi !

I am newbie to vuforia.

I am working on books sample..My requirement is to render an image on texture.

I have gone through the sample and could successfully set cloud trackables ,and parse the metadata of it.

I need help in texturing for image rendering.

my Quad.h in sample has plane vertices and normals.

I don't get why we need to store an image to render.

If someone has done this ...please do help me

Thank you..!!!