Control arms with controller

im really new to unreal engine but id like to know what i would have to do to make the left joystick on a controller control the left arm. and vice versia

You would need to have animations of your arms moving.
Then you would need to set them up in an animation blueprint. Then in your character blueprint you could get the axis value of your sticks to drive the animations.
I would suggest you to go to ue4 youtube chanel and watch all the animation blueprint tutorials.