Hello all! I am totally new to the world of animation. I’ve finally gotten my first person arm rig (rigged in A.R.T) working and now I need to attach items to my hand. I understand that I should do this by attaching it to a socket, but I have a few questions. When I attach meshes to “hand_l” or “hand_r”, the mesh is attached to the wrist (which is expected), but how do people get it in the hand? Do they move it manually? Should I create a new Leaf module? I remember seeing a couple bones on Mixamo models as well as the ThirdPersonCharacter from the samples called “ik_hand_l” or something like that. How would I go about creating IK handles? I’m really confused. In the end, I just need to be able to have my item attach to my hand perfectly. Any help? Lol thanks! 
About sockets - it’s pretty easy! Seems like you’ve missed core element of sockets workflow - sockets 
Select your “hand_l”, right click and create socket. Then in settings you can customize it further - add relative to parent bone rotation, offset and scale. It’s basically allow to have socket in a position for holding sword, for example + getting data from parent bone
Thanks for the reply! I actually found that last night right after I posted this. What is the difference between attaching actors to sockets added in Unreal and attaching actors to a socket called “ik_something”? Is it still better to create sockets in A.R.T? Thanks!
One thing you may have to do is that you might have to adjust the (0,0,0) point on your weapon model to have everything line up properly with the hand socket.
the ik_something bones are there so you always have a point of reference of where the hands should be relative to anything you applied as an additive animation. The upside of blending additive animations is one can add some interesting secondary motion but the down side is it causes other animations like aim blends to float. By adding an IK solution to the skeletal bones you can pull the hands back into their relative position.
My preference would be to add the socket in UE4 to the IK_hand_Gun as you can then animate two handed weapon reloads. (ie M4 M16 AK47)
My honest advice is to add an unskinned bone for the weapon itself in the skeleton, and use your animation software to attach the weapon to it, and constrain it to the hand while you design your animations. Then, simply attach the weapon to the “weapon” socket that represents that bone inside UE.
The major advantages of this are twofold:
(1) you can easily tweak how the hand holds each individual weapon in your animation/modeling software, rather than typing coordinates over and over by trial and error in UE, and
(2) if you ever need to animate the weapon itself (suppose you have a reload animation where the weapon needs to rotate slightly in the player’s hand, or a melee weapon that needs to roll or spin with the fingers or something) you can do so easily, rather than trying to use UE’s scripting to move the object itself relative to the socket with timelines or whatever.