You need a UserBase account before you can be added to the Translator group, register or log in here. The workflow for translators is described in Translate a Page.
Be aware that your contribution will be governed by the Gnu Free Document License and Creative Commons License, see KDE UserBase:Copyrights for details.
To request a Translator account, please post here:
Your UserBase username,
the language(s) you will work with,
It is helpful if you tell us whether you intend to use off-line translation. Off-line translation means using other tools like Lokalize and uploading ready translations here. This is for planning only, and you can change your mind.
You will get a message when your account is activated.