To be able to cast his cantrip you must be either a Hexblade Warlock or be a Warlcok with Pact of the Blade.

As part of the action used to cast this spell, you must make a melee attack with a weapon (the material component) against one creature within the weapons reach, otherwise the spell fails. On a hit, the target suffers the attack's normal effects, and and additionally suffers 1d6 Force damage.

Invocations that could be applied ot and Eldritch Blast may be applied to this cantrip as well.

This spell's damage increases when you reach higher levels. 

At 5th level, the melee attack deals an extra 2d6 Force damage to the target, at 11th level the  damage increases to 3d6 Force damage and at 17th level it increases to 2d6 Force damage.