How to move a characters lower torso?

I'm working on a way to see the characters legs I did the leg models and script but when i move the lower torso up it comes back to the old position again is there a way to make it stay there By the way i'm using a character from toolbox and there are attachments in the lower torso but i did everyting to weld it there help me.

Try using a Weld, such as:

local player = game.Players.LocalPlayer
local char = player.Character or player.CharacterAdded:Wait()
local part = Instance.new("Part")
part.CanCollide = false

local weld = Instance.new("Weld")
weld.Part0 = part
weld.Part1 = player.Character["Left Leg"] --- change leg to what u want

NOTE: Make sure you use a Script and make sure it is not a LocalScript.