There are a number of different ways to answer yes (and no!) and it depends on what the question is.
Basically, the answer echoes the question verb.
Yndw is yes to anything that starts with wyt.
Oes is yes to anything that starts with oes. (t'isio is a shortened form of oes t'isio)
And if the sentence doesn't start with a verb (e.g. "panad o de?", you should use 'ie'.
An exception is if the question is in the past tense - you can use 'do' for any 'yes' answer in the past tense regardless of the verb used in the question.