pleas help me figer out how to change my roblox model in studio?

Every player in game has a child called Character that is the player's model in game.Workspace.

The model has lots of different items inside it, including BodyColors (BrickColor values for every body part), A Shirt*, Pants* and a ShirtGraphic* (T-Shirt). The Character also has a Humanoid, with the values Health, MaxHealth, and WalkSpeed.

*If the player is wearing one

You can change all of these by simply accessing the Character, finding the object you want, and editing it's properties.

Hope I helped :)

Go into workspace, then click your character, get the shirt/pants template ID and put it in the shirt/pants or you can automate it like this:

ChangeClothes=function(p)
    wait(2) -- Wait for character to load
    p.CharacterAdded:wait() -- Extra measures
    for _,v in next, p.Character:GetChildren() do
        if v:IsA"Shirt" then
            v.ShirtTemplate="http://www.roblox.com/asset/?id=ID";
        elseif v:IsA"Pants" then
            v.PantsTemplate="http://www.roblox.com/asset/?id=ID";
        end
    end
end

game:service'Players'.PlayerAdded:connect(ChangeClothes)