Step 1: Place WorldPlacer(Prefab) in your Avatar.

Step 2: Set your Avatar Root Object (the one with the AvatarDescriptor Script on it) in the WorldPlacer Object (see "Setup-WorldPlacer-Object" picture)

Step 3: Klick on the "Switch" (WorldPlacer/Switch) and set your Armature there, like in Step 2.

Step 4: Put the Stuff you want to place in the World into the "PUT-STUFF-IN-HERE" object.

Step 5: Put the Animation File on a Gesture, Toggle State or Adv. Avatar Toggle.

Step 6: Profit