During Ludomir's first day, you'll come to an open courtyard area after exiting a large room through a door. There will be many pillars arranged in this area, along with a group of enemies. Simply head next to the most centered pillar, and use Ludomir's companion ability, and his area of effect should knock down all the nearby pillars, hopefully hitting and killing at least 4(It might just need to be 2, as the patch notes on the Steam version note they changed it from 4 to 2 at some point)enemies.
If not, you can simply restart the checkpoint, and you'll start right before the pillared courtyard to try again.