How to combine Inverse Kinematic with animations? For fps arms

I want combine Inverse Kinematic with animations, for example when i reload a weapon the left hand and fight hand there are attach ti weapon, and when play the animations Is combined. I tried much and much but nothing. Thx for answer!

The results Is this one i want:

What you want to do is to:

Install Animation Rigging (com.unity.animation.rigging) package available in the Package Manager.
Switch to Samples tab and click Import to import ready and working examples of how to setup animations with all kind of IK setups.