My biggest advice is to put them in knickers/undies as much as possible
This way they will slowly learn when they are wet and dry. Slowly learn when they are weeing/pooping.

If they do a poop, taken them, put it in the toilet. They will physically see where the poo should be going, where they should be doing poo in the first place, itms.

Its a long process.. patience is the key!

Good luck!