Visit the site for the complete info: 
or read the official info from WMent here: 

(NOTE: for now, it’s only available for korean BANAs, we’ll tell you later if we find any info regarding the vote ways for overseas fans)

And this is the translation from WMent official notice:
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21st High1 Seoul Music Awards
Hello, this is the president of B1A4’s fanclub.
I will give you a tutorial of how to vote for the 21st High1 Seoul Music Awards planning to be held on January 19t, 2012.
I humbly request all BANAs to vote for B1A4 who has been actively working hard with their promotions since their debut in April 2011.

Currently, B1A4 is a nominee for the Rookie of the Year and Popularity awards.
Please remember the Rookie awards is a very important and memorable award and only have ONE chance to win after debut. ^^
In order to make B1A4 the winners of the Rookie awards I ask for all BANA’s full cooperation.
If you’re voting via ARS,
There will be a fee of 300 won (30 cents) for every 30 seconds. In order to prevent over-spending, please see below for detailed instructions.

The 21st High1 Seoul Music Awards
Date/time: January 19th, 2010 (Thurs) 7:00P.M.
Location: Gymnastic Stadium at the Olympic Park.
Broadcasted by : KBSN
*Voting time
November 24, 2011 (Thur) ~ January 18th, 2012 (Wed)
*Voting method
(If voting via ARS, you may only vote 10 time a day)
MOBILE VOTES FOR POPULARITY
Text 3321 to NATE SHOW
Press 1 to vote for popularity awards.
Press 2 to keep track of votes.
(To vote there will be a fee of 500 won, to see current ratings there will be a fee of 100 won)
ARS Vote.
Rookie of the Year B1A4 vote
dial 060-900-0999 -Popular vote NUMBER 2 - Rookie of the year award vote NUMBER 2- *10 (B1A4’s voting number is 10)-NUMBER 1 (If this is correct)
Popularity awards B1A4 vote.
dial 060-900-0999 -Popular vote NUMBER 2 - Popularity award vote NUMBER 3- NUMBER 1 (For Korean)- *10 (B1A4’s voting number is 10)- NUMBER 1 (If this is correct)
OR
060-900-0999 - Popular vote NUMBER 2 - Popularity award vote NUMBER 3 - NUMBER 2 (For voice recognition) - B1A4 (Press * after saying it) - NUMBER 1 (If this is correct)
For more detailed information regarding admissions, please visit the Seoul Music Awards website at SEOUL MUSIC AWARDS

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Let’s hope for B1A4 victory this time, spread the word and ask your korean BANAs fellas to do the best for our boys. Hwaiting B1A4 + BANAs !!

source: seoul music awards+wment site
caps cr: AVIATEB1A4
trans cr: jiyoung @ AVIATEB1A4