This is a simple how-to on updating an AWS Classic Load Balancer with a specific TLS Negotiaion Policy. Just read the script to see how the update works.
To get a list of available predefined policies that are available execute
aws elb describe-load-balancer-policies --query 'PolicyDescriptions[?PolicyTypeName==`SSLNegotiationPolicyType`].{PolicyName:PolicyName}' --output table