You now have a new Pose Asset to use in your animations.
To preview it make sure Preview Post Asset is set to your Pose Asset, and then add a Variable Curve to your animation that needs the Pose Asset data.
You can then add keyframes to the variable curve to drive the value of the pose weights, affecting the animation.
For these to work at run time, you'll also need to include a PoseAsset node in your Anim Blueprint.
It's also worth noting you can create a Pose Asset in the Animation Editor. You can use the Create Asset -> Create PoseAsset -> From Current Pose or Animation options: