log out of city of heroes.
wait at least 5 mins.
go to plaync.com
loginto master account.
select your CoX eu account.
click upgrade account.
enter the serial code.
wait up to 30 mins.
login and use the valkyrie costume.
you should also have gotten the option when you bought it to upgrade exsisting account, if not i would really double check you didn't buy US version.
I am absoloutely sure I did not purchase the US Version
I go to upgrade account on my account and it comes up with creating a new account instead of applying it to my account.
The mac pack thing has a month free with it so that is why it wants to make a new account but I can't do it for some reason
If it doesn't upgrade buy forcing you to make a new account, the code is not compatible with your CoX account. I would contact support about it, because it would appear you bought something thats not CoX mac edition or EU.
Because once you click upgrade account and enter serial you should get three options.
one where it says something like:
[CoH logo] Upgrade an exsisting account: {name of account} then a button where it says "upgrade account".
below there should be an option to upgrade an exsisting account not listed here.
then third option would be to create a new account.
if the third option is all you see... dunno, you either didn't buy the right thing or your account is special 
Seriously contact support if you cannot upgrade it.
https://secure.plaync.com/cgi-bin/St...amp;item_id=84
copy and paste that into your url
is that the right thing? as that is what I bought
Iirc after you bought it, it asks you straight away if you want to apply the code to an account. If you do so, it will show all available accounts (if you have more then 1), hit apply and its done.
Hmm.. the secure.plaync.com website aint working here 
50)Sinergy X/(50)Mika.
(50)MaceX/(50)Encore
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Contact support, I had a similar problem (but I had followed a link US version... *blush*) and they fixed it very swiftly for me.
Ok, I bought the mac special edition just so I could get this valkyrie costume set
I have bought the european version and I have got the serial code but it only lets me make another account for it
I want too make it activate on my account I use all the time
My mates done it and now they have the costume set but I can't seem to do it! help please