You become proficient with using your shield as a weapon.

While Wielding a shield, you can use your bonus action to make an attack against a creature.  

Roll a for a normal attack, adding your proficiency bonus and strength modifier to the attack roll.

The damage is 1d4 + strength modifier.

If you attach a blade (slashing) or spike (piercing damage) to your shield, the damage die increases to 1d8 + strength modifier