I think that this part has been the most difficult step so far, even more than applying to Yonsei and for a student visa, but it didn't have to be as difficult and stressful as they made it seem. I was stressing out for no reason worrying that I wouldn't get the classes I needed.
First of all, Yonsei sent us this e-mail:
I was like, "Oh, that doesn't sound so hard," so I waited until Aug. 6 to see if I could log into the portal. I tried to log in
on Aug. 6 at 12am KST, but had no success. I tried again around 8am KST(it's not set up to open automatically at midnight, someone has to be at the office to actually open the portal) and was able to log in with the default password(birthday in YYMMDD format) they set up for me. A lot of other people were having trouble logging in, but it turned out that Yonsei had gotten their birth dates wrong.
Then on Aug. 8 at 7am KST I logged on to make my wishlist and had no problems, just remember to use IE because the portal may not work properly on another browser. I was just waiting until 10am KST to actually enroll into my classes when I saw something like this:
MAX CAPACITY:5!! I started searching everywhere to see if it was really true that only 2-5 people could enroll per class. Then I stumbled across this blog:
This girl does a really good job at guiding you through the course registration up until where she mentions that there are only 5 slots per class and that she was lucky to have gotten the classes she wanted because a lot of her friends didn't get a slot. So there I was ready to click away once the clock hit excatly 10am KST. I managed to enroll in 3/5 of the classes I wanted, and after the FIVE seconds it took me to enroll in those 3 the others said there were no more seats available! I was upset because Korean and Intro to Korean Marketing Practices were already filled up. Pretty much all the other classes taught in English said 0 seats available so I thought I was going to have to wait until the second course registration.
However, I checked again about an hour later and almost all of the classes had increased their max. capacity by A LOT! So I signed up for the two classes I was missing and felt stupid for panicking so much. I guess Yonsei just wanted to torment us by making us think the majority of us wouldn't get the classes we wanted.
I hope this saves someone in the future from panicking like I did. You'll most likely get the class you want!
UPDATE 7/21/15:
So people have told me that the registration systems is not on a first-come first-serve basis anymore. I'm not sure how it works yet, but you choose classes and then are notified which ones you made it into.