How can I install new languages on the journal website (Romanian and Norwegian)?
first check which languages are supported: https://pkp.sfu.ca/contributors/translation/#ojs-languages
To install additinal language go to Settings - Website - Languages and then Install Locale.
but there is no Romanian language on this list, what should I do?
Adding a new language is not a trivial job. Please see the chapter on page from my previous reply:
Contribute to translation
You can contribute to the PKP community by translating the software or translating documentation. For information about translating software see the PKP Translating Guide. For information about translating documentation contact us at email@example.com.