How can I trigger other clients to change their position?

Hey Guys! I would like to create a Kill System in my game the following way: In 2D when I click on the other player It should change the position. The problem: How can I solve that when I click on player, in the Killer's client I trigger something, so the PositionChange function calls on the other client who died? When I simply call the PositionChange funtion on the Killer's client it doesn't work, because it has no authority for that. I am really new in this field, so I appreciate every advice that I get.