Assess your learning style before choosing to enrol in an online learning course. Many online classes do not have structure or a teach, so it is best to ask yourself whether you learn well on your own or if you need the support of a teacher and structure of a classroom.
Find a free online language program through Busuu.com, Easyportuguese.com, or 101languages.net. These free programs allow you to move at your own pace through the lessons and interact with other students who are following the same lessons at you in chat rooms and message boards. You are required to pay for more advanced lessons.
Research the options available at your local university or community college. Some area colleges offer non-credit continuing education language classes online. Most online courses run 10 to 20 weeks and structure lessons and assessments through the week.