At Official Mu Online you get bonus for goals!
Upon reaching level 400, access the menu: Redeem Code
On the website panel and apply the code: Reward-Level-400-Win
Just copy and paste in the area indicated exactly as written here, you can't go wrong.
Remembering that it can only be used once, you automatically receive the amount of 3,000 WCoin in your account.
So don't waste time and start to level up to get to level 400 faster and receive your freebie.