While abroad, you will register via the CSU, Chico Portal just as you did when you were in Chico. Make sure to watch for an e-mail invitation in October (for Spring registration) or March (for Fall registration) or check the Chico State website to anticipate your date of registration.
The time difference from overseas can be problematic for some who are studying abroad (just a head's up). It is VERY IMPORTANT that you try your best to register during your assigned registration time if you want to get your preferred classes at Chico. As you are probably aware, the campus is experiencing massive budget cuts, and missing this date could mean not getting many of the courses you need to graduate.