How can I do this?

Animating a weapon is less related to the engine itself since you usually do this in an external 3D program. Animating a weapon (and modelling and UVMapping) can be done in a program like 3dsMax. This is software you need to pay for though (there is a 30 day trial).
If you want a free alternative, use Blender.

After you have the model, you assign bones to it and you create an animation which you then export all together to Esenthel.

For more inro, I refer to the animation/rigging tutorials of the 3D program itself. Also check the Esenthel information (you find it all bundled in the main folder) on things you should keep in mind for Esenthel specific animations.

I know. How to play animation of weapon in game? Basic Item class don't support controlled skeleton, I tried to remake it based on the "Animation" tutorial, but...

You have to write your own animation handler to support it. Every model can have a skeleton you just need to code a class with a Mesh + Skel. Weapons are no items or whatsoever... they are just models that the player sees based on the item the player has equipped...

Thanks, I solved the problem...