Improve AWS single-tier documentation

userguide/aws/how-to-login-to-your-ec2-instance.adoc

@@ -0,0 +1,33 @@
+= How to Log In to Your EC2 Instance via SSH
+
+:card-badge: Premium
+:card-title: AWS Deployment
+:card-link: https://aws.amazon.com/marketplace/pp/prodview-jvcsq4phzaclw
+:card-description:
+include::{sourcedir}/includes/premium-card.adoc[]
+
+== Overview
+
+Logging in to your EC2 instance is *not required* to run Kill Bill — it is only needed if you want to perform configuration, maintenance, or troubleshooting tasks directly on the instance. This applies to the Single-Tier, Multi-Tier, and CloudFormation AWS deployments.
+
+To log in, you need:
+
+* A *key pair*, created or selected when you launched your instance. The private key file must have been downloaded and saved, and its permissions set so it is readable by the owner only.
+* An inbound rule in your instance's security group allowing *SSH* access on port `22`.
+* The *public IPv4 address* of your instance, available on the EC2 *Instances* dashboard.
+
+== Logging In
+
+To login, use the secure shell command:
+
+`ssh -i PRIVATE_KEY.pem ubuntu@INSTANCE_IP`
+
+Here PRIVATE_KEY is the pathname where you have stored the private key that was downloaded when you generated your key pair, and INSTANCE_IP is the public IPv4 address of your instance. The private key will not work unless its access controls are set to readable by the owner only.
+
+On Windows versions before Windows 10, you may need to download a program called PuTTY to enable `ssh`. On Windows 10 and 11, `ssh` is available but may need to be activated through the Settings screen.
+
+The first time you login, you will see a warning message asking if you want to add this host to your list of hosts. You should answer `yes`.
+
+You will now be able to explore your instance and perform various configuration and maintenance tasks. To exit from your login, type `exit`.
+
+NOTE: If you only opened the SSH rule temporarily to perform a maintenance task, consider removing it from your security group afterward to reduce your instance's exposure to the internet.

userguide/aws/how-to-maintain-a-single-tier-system.adoc

@@ -12,7 +12,7 @@ This guide explains how to maintain your single-tier Kill Bill installation on A
 
 == Log in
 
-To perform most maintenance tasks you will need to log in to your EC2 instance. Be sure that SSH is enabled on Port 22 in your security group. Login procedures are described in the setup guide  (See https://docs.killbill.io/latest/how-to-set-up-a-single-tier-system.html#step_7_login_to_your_instance[Step 7: Login to an Instance])
+To perform most maintenance tasks you will need to log in to your EC2 instance. Be sure that SSH is enabled on Port 22 in your security group. Login procedures are described in https://docs.killbill.io/latest/how-to-login-to-your-ec2-instance.html[How to Log In to Your EC2 Instance via SSH].
 
 
 == Troubleshooting