Prerequisite: Launched your first instance from Portal.
Step 1: Navigate to the region that your instance is created.
Note: Security Groups setting differ by region.
Step 2: Go to the Security Groups tab and click Manage Rules to edit your rules.
Step 3: Add a new rule to your Security Group.
Step 4: Set the rule by allowing port(s) according to your use-case.
Step 5: To associate the edited security group to instance, go back to the Instances tab, can click Manage Security Groups under the More dropdown option.
Then, select the Security Group that you want to assign to the instance, click Update.
The specific port will be allowed to connect to your instance from external.