Enroll in an online Quranic Arabic course offered by your local university or community college, or by an educational institution located elsewhere which allows online or "distance" learning. Clicking the various links listed under "Resources" will take you to the websites of institutions which offers these types of courses, including the "Islamic Association of North Texas," "E Aalim Online Institute" or "Quraan-ic Lessons."
Complete assignments and assessments diligently and with integrity. Although taking a language class online may result in temptation to cheat on assignments and assessments using the many Internet dictionaries and resources you have at your fingertips, doing so will prevent you from acquiring enough of the language to use.
Test and build upon your understanding by reading regularly from an Arabic-language version of the Quran. Don't be shy about contacting your online professor or advisor with questions, either as they pertain to the course materials or the Quran itself. One advantage of learning Quranic Arabic is that all your course material will have a real-life context you can use to enrich your learning experience.