Hi,
No worries.
If you want your text to be in different languages, like the rest of the email, then you need to add a translation in the override file by edit the languages under the Languages tab of the HikaShop configuration. Then, edit the email, and in the "preload" section, you'll need to add a code line like:
'XXX' => JText::_('XXX'),
after the line:
'BILLING_ADDRESS' => JText::_('HIKASHOP_BILLING_ADDRESS'),
where XXX is the translation key you've used to add your translation to the override file.
Then, in your email, you can use {TXT:XXX} and HikaShop will replace it by your translated text automatically when generating the email.