Lewis Dot Structures show atoms and their valence electrons. Valence Electrons can participate in Bond Formation.
A chemist working with Lewis Dot Structures also uses the Periodic Table, the Octet Rule and Formal Charge.
Hydrogen has one electron. It is a valence electron and it is available for sharing to form a single bond.
Carbon has four valence electrons and it can form single bonds and multiple bonds to get the four more bonds that it needs.
Rob Sterling 