Hi@akhtar,
You can attach one or more Classic Load Balancers to the specified Auto Scaling group. Amazon EC2 Auto Scaling registers the running instances with these Classic Load Balancers. The below example attaches the specified load balancer to the specified Auto Scaling group.
$ aws autoscaling attach-load-balancers --load-balancer-names my-load-balancer --auto-scaling-group-name my-auto-scaling-group