I can't set up the failover in the load balancer

I can’t set up the failover in the load balancer, I need help with your product. The goal is that when the primary server is down, the secondary server should take over. Please give a demo, I have referred to your document it’s useless.

I have two public IPs with two domain names. Please set up a demo and share the screenshots.

Demo here…

how to set up failover “Active-passive”.