Once created, you will be returned to the Security Groups section where you can add rules to the security group by clicking the Manage Rules button of the corresponding group:

To delete a rule, click the red Delete Rule button next to the corresponding security group rule. To add a rule, click on the Add Rule button in the upper right-hand corner:

A window will appear that will allow you to create rules. Within the rule list, you can choose from a predefined list of protocols or create a custom rule as follows:

The wizard allows you to specify the direction, port or range of ports, and the remote network or group. To complete the rule creation process, click on the blue Add button.