'furthermore' can be used as an adverb to mean in addition to, or what has been said before.
make sure the sentence is linked to the one before it, as this is how to make sure the word is used correctly. It is important to note that this word cannot be used at the beginning of a sentence, since it is not a transition word.
'The accused denied the charges. Furthermore, he denied any involvement whatsoever.'
tips for using this word are to pay attention to the nature of the sentence and the connection to the sentence preceding it to make sure it is the correct word choice.