AWS Getting Started - Configuring Security Groups
It is strongly recommended to limit traffic to your SoftNAS instances to known IP addresses, to ensure security. As it is strongly recommended to use the internal IP address when configuring SnapReplicate™ and SNAP HA, and because you will not yet have the internal IP addresses of your instances when creating the initial instance in an HA pair, it may be more expedient to configure the security group after instance creation. If you have restricted HTTPS traffic to your local IP address, you may need to later alter the Security Group if your local IP address changes, as this restriction may prevent access to your instance.
Select the instance in question from the EC2 Console, under Instances.
Then find the Security Group column by scrolling all the way to the left, and click the Security Group.
This will open the Security Groups panel, with the security group used for the instance already selected. (If you opened Security Groups from the EC2 dashboard menu, you would have to search the correct security group from the full list of available security groups.)