How would I make a ScreenGUI pop up when a player enters a specific area?

This isn't like a GUI button, but an area that if a player enters, a ScreenGUI comes up

I think the best way is indeed to make an area, set the area part to cancollide false and transparency to 1 so it is invisble.

You then right this code in a local script inside that part:

local area = script.Parent

local players = game:GetService("Players")

area.Touced:Connect(function()

players.LocalPlayer.PlayerGui.YourGui.Enabled = true

-- players.LocalPlayer.PlayerGui.YourGui.Visible = true -- when using Visible

end)