Updated with autoplay mention

Copy of this stale PR: godotengine#6392 (comment) rebased. Both can be closed now.

Author: Vennnot

getting_started/first_3d_game/09.adding_animations.rst

@@ -257,10 +257,12 @@ node structure, you can copy them to different scenes.
 For example, both the ``Mob`` and the ``Player`` scenes have a ``Pivot`` and a
 ``Character`` node, so we can reuse animations between them.
 
-Open the ``Player.tscn`` scene, select the ``AnimationPlayer`` node and open the "float" animation.
-Next, click on **Animation > Copy**. Then open ``Mob.tscn`` and open its animation
-player. Click **Animation > Paste**. That's it; all monsters will now play the float
-animation.
+Open the *Player* scene, select the AnimationPlayer node and open the "float" 
+animation. Next, click on **Animation > Copy**. Then open ``Mob.tscn``, 
+create an AnimationPlayer child node and select it. Click **Animation > Paste** 
+and make sure that the button with an "A+" icon (Autoplay on Load) and the 
+looping arrows (Animation looping) are also turned on in the animation editor 
+in the bottom panel. That's it; all monsters will now play the float animation.
 
 We can change the playback speed based on the creature's ``random_speed``. Open
 the *Mob*'s script and at the end of the ``initialize()`` function, add the