Telling Weblate what languages you understand/translate will make it easier afterwards. You can also take a moment to edit your account profile and settings if needed.
The Framasoft GitLab instance is hosted at framagit.org. You have to sign-up here, using your e-mail account or by way of a third-party token provider.
Weblate will now present you with text in need of translation or correction. Confidently submit a translation, or fill-in your proposal and submit the form. If you're not sure at all, comment or move to the next string.