The Forms are not physical items: they are entities that exist somewhere in the center of the universe. Plato uses the concept of beauty to explain this. A flower may be beautiful and a chair may be beautiful. What they have in common is that they both participate in the higher realm in the Form of beauty. The chair also participates in the higher realm of the Form of Chairness, and the flower of Flowerness.
Particular objects in the physical realm participate in the Forms and are what they are by virtue of this participation.
The highest form is that of perfect goodness (a combination of Love/Justice. Plato calls this The Good, though in some writings translators call it the Demi-urge or God. (however, the Judeo-Christian concept of God was not known by Plato. All Forms are perfect, and they get their perfection by participating in the Good itself.
Knowledge of the Forms is acquired through intuitive recollection. We are born with ALL knowledge (participating in the Forms and The Good, but we forget it all at birth. All knowledge is buried deep in our memory and minds, and we can use rational thinking to tap into know.