First, I must assume you are the team founder (or have been given admin rights by the team founder).
If this is a BOINC-wide team, go to the BOINC-wide Teams page
HERE and log in (top-right corner). If not, you will need to log into each individual project's website and do the following:
1) Scroll down and click the link "Your Account"
2) On the right side of the page, in the Community box, click the link "Administer"
3) At the top of the page click the link "Edit Team Info"
4) Near the bottom of the page, use the drop-down menu to Select "France," the click the "Update Team Info" button.
You're done! If this is a BOINC-wide Team, allow at least 24 hours for the updated description to populate to the individual project servers. If you are updating individual projects, the description change should be immediate.
Hope this helps!