How can I make a door that only players in a certain group can open?

One of these scripts goes inside of a LocalScript. The LocalScirpt should then go into StarterPlayerScripts. Both scripts just loop through the PartLocations table and makes the parts uncollide, this only happens locally.

This script shows you how you would use GetRankInGroup(). Documentation about this can be found here https://developer.roblox.com/en-us/api-reference/function/Player/GetRankInGroup

local PartLocation = { -- Insert the paths to the parts in this table
	
}

--[[Example Table
local PartLocation = { 
	workspace.Part,
	workspace.Part2
}
--]]

local GroupID = 1 -- Your GroupID
local RanksAllowed = 2 -- Everything above the rank of 2 in the group can use the door

local PlayerService = game:GetService("Players")
local Client = PlayerService.LocalPlayer

for index, part in pairs(PartLocation) do
	if Client:GetRankInGroup(GroupID) >= RanksAllowed then
		part.CanCollide = false
	end
end

If that isn't what you meant then perhaps you meant anyone inside of the group? If that is the case we will be using IsInGroup() https://developer.roblox.com/en-us/api-reference/function/Player/IsInGroup

local PartLocation = { -- Insert the paths to the parts in this table
	
}

--[[Example Table
local PartLocation = { 
	workspace.Part,
	workspace.Part2
}
--]]

local GroupID = 1 -- Your GroupID

local PlayerService = game:GetService("Players")
local Client = PlayerService.LocalPlayer

for index, part in pairs(PartLocation) do
	if Client:IsInGroup(GroupID) then
		part.CanCollide = false
	end
end