Merge remote-tracking branch 'origin/doc/10970-screen-locker' into testing

Fix-committed: #10970

wiki/src/doc/first_steps/introduction_to_gnome_and_the_tails_desktop.mdwn

@@ -4,7 +4,7 @@ The desktop environment used in Tails is [GNOME](https://www.gnome.org).
 This page describes some important features of the desktop in the context of
 Tails.
 
-[[!toc levels=2]]
+[[!toc levels=3]]
 
 Top navigation bar
 ==================
@@ -190,6 +190,20 @@ manage your systems settings and your computer.
 
 </div>
 
+### Locking your screen
+
+Click on the <span class="button">[[!img lib/network-wireless-encrypted.png alt="" class="symbolic" link="no"]]</span>
+button in the system menu to lock your screen with a password.
+
+- If you set up an [[administration password|first_steps/startup_options/administration_password]]
+  when starting Tails, you can unlock your screen with your administration
+  password.
+
+- Otherwise, you can set up a password to unlock your screen when locking your
+  screen for the first time.
+
+  [[!img screen-locker.png alt="Set a password to unlock your screen" link="no"]]
+
 <a id="activities"></a>
 
 Activities overview