If you just want to spawn a Cube mesh in a level then in blueprint you can do:
- “SpawnActorFromClass” node
- Assign it the Class “StaticMeshActor”
- Plug a make transform node into the SpawnTransform property
- Plug the return value into a SetMesh function of its StaticMeshComponent
- Set the NewMesh property to a cube mesh. Several come with the Engine content