I will start by saying I don't know Arabic. I do know 4 and speak 3 different languages. The easiest way to learn a new language is when it has a relation to the language you already know. I don't know if Arabic has a relation to the languages you already know but if you're looking for a place to start I'd go to Duolingo. I've only heard good things about it, but haven't used it myself yet. Other then that I'd say watch movies in Arabic with subtitles in English and later the other way around.