You can use one of the English-Latin dictionaries, or some other vocabulary, to find a Latin equivalent of an English word, but unless the Latin word you find turns out to be one with which you are very familiar, you should get in the habit of looking up the Latin word in Lewis and Short (or the Oxford Latin Dictionary if you have access) to make sure that the Latin meaning is the same as the English meaning you're searching for and that you're using the word in question properly. For example, you need to make sure you're putting any noun complements of a verb in the right case, using the right prepositions, not using an intransitive verb transitively, not using an exclusively poetic word (or not using a word in a poetic meaning) in writing prose, making sure that the word is used in the Classical period, not in the archaic period or late antiquity, etc.
Don't use a less authoritative Latin-English dictionary like Cassell's for this purpose. You need one with actual citations to specific passages.
Lewis and Short is on line: http://perseus.uchicago.edu/Reference/lewisandshort.html
You should go through this exercise when trying to write any language in which you're not a native speaker, or at least very fluent, including modern languages. It's all too easy to go astray and write something completely ridiculous if you're not careful.