How to make a player get a badge when they get a gamepass?

Use game.Players.Playeradded and do a check if the player possesses the gamepass. If they do then use Badgeservice to award them the badge. If ur still confused il elaborate more An example can be that

local BadgeService = game:GetService("BadgeService")
local MarketService = game:GetService("MarketPlaceService")
game.Players.PlayerAdded:Connect(function(plr)
local Possesessgamepass = MarketService:UserOwnsGamePassAsync(plr.UserId, insert ur game pass id here)
if Possesessgamepass == true then
BadgeSerivce:AwardBadge(plr.UserId, badge you want to award id)
end
end)