How to add strings

Hi,

On the top right of my website’s nav, there is a button “participer(fr)/contribute(en)” and both links send to the french page.
I want the english one send to the english page, so translate the link of the button.

I know that functions exist but if someone can help me to put the function associated to my needs, it would be so great !

Thanks a lot !

The page I need help with: [log in to see the link]