Dwarfs are unable to cast spells, and have no wizards.
During the magic phase, the Dwarf player is dealt magic cards as usual, though he may only make use of the Dispel and Drain Magic cards. Because Dwarfs have such a high resistance to magic, Dispel cards always work on a roll of 4+. The rules for Dwarfs using magic cards and dispels are given in full in Warhammer Battle Magic.