Manipulate the Mannequin bones

Hi, i am new to Unreal Engine and found no relevant info here.

I want to move specific bone using default mannequin with code like visualised “LowerArm_Left” in figure.
Which class is responsible for this or i should do it manually? If so, how to call mannequin object? I would be very grateful if you can provide an example like:

Project1->SK_Mannequin->LowerArm_Left->Rotate += 1;