Load balancer says Unknown host. I need help getting this configured correctly so it is not critical health

I just setup the load balancer and I am getting Load balancer says Unknown host. I need help getting this configured correctly so it is not critical health.

I have added my host URLs. Doesnt the load balancer function just create that from those domain options or do I have to add stuff to DNS? Also, I cant find the intro help instructional video link anymore can you send?