Alpha mask

[OoAnikioO]

Hello, I make posters of which some objects on it should not be edited at all, my wf is to have a poster for example with a character and a necklace that I have rendered with 3dsmax, the character is simple, then I create an alpha mask of the necklace
I would therefore like in krita, load the full poster, the alpha, is therefore, only change the character who must also follow the same pose, so there would probably be controlnet

How to do that? How do you add loras?

Thank you