Please note: If you want to edit the animation length, firstly select the imported FBX file, go to the inspector panel and select animation (see image below). From here you can crop the animation using the slide bars or by setting the frame start and stop values. Note unlike the other platforms you cannot extend the animation this way (i.e. add extra keys), you can can only remove keys.
The PlayerArmature prefab has a default Base Animation Layer below.
In the Inspector edit the mask from the default to only the Hands being active (green)