There are two times you can vote for Music Core: During the live show and pre-voting. Here is the tutorial for both of these systems^^
Music Core (during Live show)
+You can vote for your group during the broadcast time of Music Core only if they are up for an award.
+To vote, you need to be able to send a text message internationally. If you are not capable, use a free, text message service online such as Slide SMS or another service like globFONE. A simple Google search can help you find the right service for you.
+1. Send a text message to 00820505 (+820505 for international) in the following format:
Your Group Name, XXXX
The XXXX should be replaced with any of the other top four artists names in hangul. Google the groups name to get the hangul, and do not put a space between the two groups names.
You must vote for two of the top four artists. You can choose any other artist, but if you do not include a second artist as shown in the format above, your vote will not be counted.
Do not vote more than once from the same device or phone number. This causes points to be deducted, and you will actually be hurting their chances of winning! If you use an international texting app, still only use it once! There is a chance its number will repeat.
+2. You can also vote, with the same account, on Mnet Korea! (goo.gl/ptU0Tz). Just look for your group's album and click the check box next to it, and then the big box at the bottom!
Music Core (pre-voting)
+To vote for your group ahead of time, you can do so by going to IMBC’s website.
+1. To go to Music Core (http://goo.gl/f6P2wI)
+2. Please follow the instructions on images 2-6.
+3. After that, please go to here: (http://goo.gl/h7WIdD)
+4. Check the box next to your group's name, as well as (3) more boxes (you have to choose 4 total), and then click the big pink button at the very bottom to cast your vote.