How do I Tween a gui from an onTouched function?

First and foremost, this should be inside a local script since this script has the job of manipulating guis. Because of this, the script should also be in the StarterGui.

In addition, line three where you declare the frame variable is wrong because you are referencing the gui inside of the StarterGui when you should be doing it from the PlayerGui. Don't get confused between the two. StarterGui is like a container that you can put your guis in. When a player joins, the contents of StarterGui are automatically cloned into the player's PlayerGui. Each player has their own individual PlayerGui. What is being shown to each player is the PlayerGui and not the StarterGui.

Finally, there are some minor improvements that can be made to the function itself such as adding a debounce and checking if the the part that touched the brick is a character.

local debounce = false
local part = workspace.Part --Whatever you want to trigger the touched event

function onTouched(hit)
    if not debounce and game.Players:GetPlayerFromCharacter(hit.Parent) then
        debounce = true
        part.CanCollide = false
        local frame = script.Parent.ScreenGui.Frame
        frame:TweenPosition(UDim2.new(0.5,-175,0.5,-11),'Out','Quint',1)
        frame.Selfie.Image = "rbxassetid://1244936009"
        frame.Talker.Text = "You:"
        frame.Message.Text = "Hello, Anybody here?"
        wait(4)
        frame.Message.Text = "Guess No-One is here..."
        wait(4)
        frame.Message = "Im Hungry..."
        wait(3)
        frame.Selfie.Image = "rbxassetid://90267225"
        frame.Talker.Text = "Server:"
        frame.Message.Text = "Go into town and get something to eat."
        wait(5)
        frame:TweenPosition(UDim2.new(0.5,-175,10,11),'In','Quint',1)
        wait()
        debounce = false
    end
end

part.Touched:Connect(onTouched)

Assuming you're using a local script (which you should be doing or else the script will tween to every player in the game) then do this

local frame = game.Players.LocalPlayer.PlayerGui:WaitForChild("ScreenGui")

now i know how to do it, i have two options in this script, they are two buttons, option 1 and option 2. im trying to use an if function but it wont work. it is supposed to be this:

local debounce = false
local part = workspace.Fragilistic --Whatever you want to trigger the touched event

function onTouched(part)
    if not debounce and game.Players:GetPlayerFromCharacter(part.Parent) then
        debounce = true
        local frame = script.Parent
        frame:TweenPosition(UDim2.new(0.5,-175,0.5,-11),'Out','Quint',1)
        frame.Talker.Text = "???"
        frame.Message.Text = "Roar!"
        frame.Selfie.Image = "rbxassetid://453541880"
        wait(5)
        frame.Selfie.Image = "rbxassetid://1244936009"
        frame.Talker.Text = "You"
        frame.Message.Text = "~thinking~"
        frame.Option1.Text = "Run"
        frame.Option2.Text = "Say 'Who's there?'"
        if frame.Option1.Mousebutton1click:Connect(function()
                --script--
else if fame.Option2.MouseButton1Click:Connect(function()
        --script--
        end)
        wait(10)
        frame:TweenPosition(UDim2.new(0.5,-175,10,11),'In','Quint',1)
        wait()
        debounce = false
    end
end

part.Touched:Connect(onTouched)

but it wont work, i know this isnt part of the question, but if it could be answered that would be great!