Open sidebar-browse.php
, find this line:
wp_nav_menu( array( 'container' => '', 'theme_location' => 'mini-first', 'items_wrap' => '<ul class="normal-list"><li class="'. $page_state .'"><a href="'. esc_url( home_url() ) .'" title="'. __('Go Home', 'acosmin') .'">'. __('Main Page', 'acosmin') .'</a></li>%3$s</ul>' ) );
Change:
__('Main Page', 'acosmin')
with __('Your French Word', 'acosmin')
Or you can translate the entire theme by using the .po files located in ../languages/
folder:
http://codex.wordpress.org/Translating_WordPress