Good evening. I have made a humanoid rig and wish to add an IK Controller to the bone "UpperArm.R". I wish to make the bone "CTRL_1.R" bone as a controller bone. Whenever I do so, the control bone snaps to the bone "UpperArm.R". A blend file has been provided. Please look into this. Thank you.
Your problem has a very simple answer. When ever you add IK control to a rig, the default chain length is usually $0$ and the bone tries to point at the rig's origin, thus creating some weird posture.
You can solve this by adjusting the chain length to the number of bone you would like to be influenced by the inverse kinematics(IK).
Try $1$ or $2$ and get a feel of what work best for the rig.