You already saved the ban when using that event. However, if you want to kick the player when he joins the player again you would try the following:
game.Players.PlayerAdded:Connect(function(plr)
local Data
local s, e = pcall(function()
Data = BannedPlayers:GetAsync(plr.UserId)
end)
if s and Data then -- if the request is successful and the data is valid.
plr:Kick()
elseif not Data then
print("No data found")
else
error(e)
end
end)
Again, do your research on Datastores and Roblox server-client model because you seem to not understand it very well (from what I can see in the past replies),