We're working on a profile updating tool for the typical user and should have it out in the next couple of days.

In the meantime, if you're somewhat tech savvy, you can update your profile as follows:

1) download/install Namecoin-Qt or Namecoind

2) use the OneName profile builder and grab the JSON

3) calculate your WIF formatted private key from the passphrase (just a sha256 then a conversion to base58check - you can use https://github.com/halfmoonlabs/coinkit for that)

4) import your WIF into your namecoin client (you should now see the username in your possession)

5) perform a "name update" operation with the new JSON profile data