Create a new actor class. Add a skeletal mesh component to it. Select the component and in the details panel change the mesh to your knight.
Spawn actor (your new actor) … done.
I wouldn’t use tick event to spawn your knights, unless you want thousands of them in a very short period of time. I’d use Set timer by Event (looping).
You can spawn a skeletal mesh into the level that isn’t associated with any existing actor by selecting “Skeletal mesh actor” as the SpawnActor class and setting the skinned mesh of the skele mesh component