How to modify a sockets transforms using Blueprints?

I’m trying to modify the shoulder socket for my character through the characters blueprint so I can rotate the arm.

What I’m trying to achieve is when the user left clicks the mouse, his arm will raise to shoot his gun. What’s the best to achieve that and how do most games do it?

There is a node for getting a sockets transforms but how do I modify them?

Any help is appreciated, thanks!