docs(README): add installation section

README.md

@@ -50,6 +50,77 @@ We want to provide a similar experiance as the [Manjaro Sway Edition](https://gi
 
 Guide used: [systemd integration - Managing user applications with systemd](https://github.com/swaywm/sway/wiki/Systemd-integration#managing-user-applications-with-systemd)
 
+## Installation
+
+### Method A: Custom Image via Live-ISO
+
+Download the Vanilla OS 2 Orchid Live-ISO, flash it to your USB stick and boot from it.
+
+You will see the following dialog:
+
+![The Vanilla OS installer shows the dialog "Welcome to Vanilla OS!" together with the four buttons "Install" and "Install Custom Image (Advanced)" as well as "Recovery" and "Power Off".](./docs/images/installation-method.png "Installation Method")
+
+Select `Install Custom Image (Advanced)`.
+This installation method differs in one step from the `Install` method:
+You can choose the Vanilla OS Image which will be installed by the Vanilla OS Installer.
+
+At some point, you will see the following dialog:
+
+![The Vanilla OS installer shows a dialog where the user can enter the URL of the custom image.](./docs/images/installation-image.png "Custom Image")
+
+Enter the URL `ghcr.io/develangel/desktop-sway:latest`.
+
+![The Vanilla OS installer shows a dialog to inform the user that the installation has finished and it is time to reboot.](./docs/images/installation-finished.png "Vanilla OS Installation finished!")
+
+After installing Vanilla OS, you can follow the [First Setup guide](https://docs.vanillaos.org/handbook/en/first-setup) to set up your system.
+
+![The First Setup shows a welcome dialog.](./docs/images/first-setup-welcome.png "Welcome to the First Setup guide")
+
+![The First Setup shows a dialog to inform the user that the first setup has finished and it is time to reboot.](./docs/images/first-setup-finished.png "First Setup guide finished")
+
+After the First Setup has finished, reboot the system and the First Setup will install the applications.
+
+After reboot, it is time to set your password. [**NOTE**: Keep the Gnome session active. Do *not* switch to the Sway session!]
+
+![The login screen is shown and forces you to set your password.](./docs/images/first-setup-reboot-change-password.png "Password Change")
+
+After login, the First Setup installs the previously configured applications.
+
+![The First Setup requests your password for authentication.](./docs/images/first-setup-reboot-auth.png "Authentication Required")
+
+![The First Setup installs applications like org.gnome.Calculator.](./docs/images/first-setup-reboot-finalizing.png "Finalizing - Installation of Applications")
+
+![The First Setup has finished the finalizing step.](./docs/images/first-setup-reboot-finalizing-done.png "Finalizing - Done")
+
+After the First Setup has finished the finalizing step, the Tour dialog pops up.
+
+![The Tour dialog is shown and wants the user to take a short tour.](./docs/images/tour.png "Tour")
+
+Now, it is time to reboot and you are done. Let's switch to the Sway session...
+
+
+### Method B: Change the image in ABRoot
+
+If you have installed Vanilla OS with the `Install` method,
+you can point ABRoot to the custom image to use it.
+
+- Open the terminal `Black Box`.
+- Edit the configuration file with the command: `abroot config-editor`.
+- Change the "name" entry from something like `vanilla-os/desktop` to `develangel/desktop-sway`.  [**Note**: All characters must be in lowercase.]
+- Change the "tag" entry to `latest` to use releases, only.
+- Now, run `abroot upgrade` to switch to the custom image.
+- Reboot.
+
+After reboot, you can select the `Sway` session when you log in.
+
+
+### Switch to the Sway session
+
+![The Vanilla OS login screen is shown. After selecting the user account, a settings button is visible. Using this button, the Sway session can be selected.](./docs/images/login-sway.png "Login with Sway session")
+
+Select the `Sway` session when you log in the next time.
+
+
 ## Build
 
 > [!NOTE]