I need help whit a script for automatic group promotion?

I have an automatic promotion system found but I need an access key to put in does anyone knows what this means

local base = 'http://roblobots.cf'
local http = game:GetService'HttpService'
local group = 4149520
local access_key = ''
local private_key = [[-----BEGIN PRIVATE KEY-----

-----END PRIVATE KEY-----]]
local send = function(action,player,...)
    local parameters = {...}
    return http:PostAsync(base..'/receiver.php',http:JSONEncode({
        action = action,
        group = group,
        player = player or nil,
        access_key = access_key,
        private_key = private_key,
        parameter1 = parameters[1] or nil,
        parameter2 = parameters[2] or nil,
        parameter3 = parameters[3] or nil
    }))
end

local promotePlayer = function(plr)
    send('setrank',nil,2)
end