Language/Translation for blog elements

Hi,

I am testing your Seasonal theme on my local server and so far everything is going well.
The only problem I am facing is that the website I am working on is in French, and all the blog elements appear in English.
For example : “Previous Article”, “Next Article”, “Posted on”+date in French, “Find” (in the search box widget), etc.

My wordpress is installed in French but I suppose this comes from the theme ?
Do you have any idea on how to translate theses litle elements ? Do I need to make a child theme or does it exist any css trick, or… ?

Thanks a lot !