Successfully change another player's stats

Hello everyone, I can’t manage that when the player presses the button which is on a seller’s widget, I can add lives to another player, example: when I press the button I add 3000 life to a blueprint type character which already has 1000 life which will make 4000. if someone has the solution I will be really happy I’ve been disappointed for several days and I can’t find anything. I think that with a BPI it can work but I don’t understand how to do it, and chatGPT doesn’t help me more than that.
thank you in advance