First use Duolingo to learn Italian. Then start buying copies of books from the Loeb Classical Library and read the Latin and English text. Then read the Latin, noting the words you can't recognise and study them. Then read the Latin again. Once you can read one book buy another one. You will not learn to write Latin this way but you will end up able to read it.

Or you could try these. I vouch for none of the below free websites. The time investment needed to learn a language is insane and textbooks are cheap, especially secondhand.

http://www.learnalanguage.com/learn-latin/

https://www.lingq.com/learn-latin-online/

http://surfacelanguages.com/language/Latin

Neither online nor free, but the Cambridge Latin courses are justly acclaimed as classics in the Classics.

Udemy has an introductory course: https://www.udemy.com/an-introduction-to-classical-latin/

Latin is a dead language, dead as it can be. First it killed the Romans, now it's killing me.