Take electronics courses by signing up either for on-campus or online electronics programs, and by fulfilling the requirements of those programs (for example, by fulfilling prerequisite requirements). Oxford's Department of Continuing Education, Cleveland Institute of Electronics, MIT and North Seattle College are four schools with electronics courses.
As of October 2015, Oxford University's Department of Continuing Education offers an Online Introduction to Electronics to students across the globe, including the United States. You can enroll in this and other online courses through the university's Enrol system, for which you need a personal account to access the system. You can create the account on the website.
The Cleveland Institute of Electronics has Automation and Robotics with Lab, Broadcast Engineering - New Mobile Media, Electronics Engineering, Electronics Technology and Lab, and Electronics Technology with Digital Microprocessor Lab among its electronic course offerings. These courses are all available online.
Practical Electronics is a free online course from the Massachusetts Institute of Technology's Open Courseware program. The course comes with a syllabus, lecture notes (available in PDF format), assignments and an image gallery.
You can take electronics courses on campus at North Seattle College. Programs include Aviation Electronics, Broadband Cable, Healthcare Tech Management, IT Controlled Electronics and Telecommunications