Hello Everyone! I have already bought a dog, and I wanna train him go to the toilet, but I don't know how to do that, someone give me a advise! thanks a lot!

Do you mean toilet training or teaching it to toilet on command?
Toilet training Consistency is key. Take pup outside to toilet after eating, playing and sleeping and at first every hour or so. When you take it out stay out there with it to make sure the puppy isn't getting distracted and when it goes to the toilet praise the puppy. If it doesn't go to the toilet after 10mins bring it back in and watch it like a hawk for any sniffing or circling. If u miss the signals or its a sort of pup that just goes and you catch it going toilet inside just pick the pup up and whip it outside to finish off. Don't punish it for going inside the house or it will likley just start hideing away to toilet and it then won't toilet infrount of you. At Times when you can't watch the pup contain it somewhere accidents are easy to clean up. Make sure it offer toilet time just before you leave when your going out. If you do that any accidents will be limited to If your not watching the puppy.

To teach a toilet command, when your out with it to toilet as soon as you see it start to toilet say what ever you want your command to be then praise while it's going and reward once the pups finished. Eventually it will learn when you say the commands it's time to go toilet if it needs to.

You state you have already bought a dog, it would also be easier for us to give a reply if we know how old the dog is.