Carbon is the central atom, the two oxygens are bound to it and electrons are added to fulfill the octets of the outer atoms. Complete the valence shell of the outer atoms in the molecule. Place any remaining electrons on the central atom. There are no more electrons available in this example. If the valence shell of the central atom is complete, you have drawn an acceptable Lewis structure.
Carbon is electron deficient - it only has four electrons around it.
This is not an acceptable Lewis structure. If the valence shell of the central atom is not complete, use a lone pair on one of the outer atoms to form a double bond between that outer atom and the central atom. Continue this process of making multiple bonds between the outer atoms and the central atom until the valence shell of the central atom is complete. The central atom is still electron deficient, so share another pair. The bond order is equal to the number of bonds between two atoms.