As far as we know, poisonous frogs in general acquire their toxins from their diet. These toxins are called alkaloids and are produced mainly by plants and insects (which are ingested by frogs, which then incorporate the alkaloids). So, toads do not manufacture their toxins, they acquire them.
Just two years ago, it was reported that an Australian frog is able to manufacture its own alkaloids. That species is, to my knowledge, the only vertebrate known to manufacture poison.