Add a section about graphical environment in terminal app

Bug: 380763330
Change-Id: I773b5d50ab44f7f07f3efe47b8165668edfc2d2a
Test: n/a
diff --git a/docs/custom_vm.md b/docs/custom_vm.md
index 9a9ede4..eaff2a4 100644
--- a/docs/custom_vm.md
+++ b/docs/custom_vm.md
@@ -24,3 +24,22 @@
 
 The `vm` command also has other subcommands for debugging; run
 `/apex/com.android.virt/bin/vm help` for details.
+
+# Terminal app
+## Graphical environment (Wayland, VNC)
+By installing Wayland compositor and VNC backend, you can enable graphical environment.
+One of the options is `sway`, `wayvnc` and `xwayland`(if necessary).
+
+```
+sudo apt install sway wayvnc xwayland
+WLR_BACKENDS=headless WLR_LIBINPUT_NO_DEVICES=1 sway
+WAYLAND_DISPLAY=wayland-1 wayvnc 0.0.0.0 # or use port forwarding
+```
+
+And then, connect to 192.168.0.2:5900(or localhost:5900) with arbitrary VNC client.
+Or, `novnc`(https://github.com/novnc/noVNC/releases). For `novnc` you need to install
+`novnc`, and run `<novnc_path>/utils/novnc_proxy`, and then connect to `http://192.168.0.2:6080/vnc.html`
+(or `localhost:6080` if port forwarding is enabled.)
+
+`weston` with VNC backend might be another option, but it isn't available in
+Debian package repository for bookworm.
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