Problem with language and integration of plugin

Hello community,

I tried to create a single page that used wishes to subscribe to my assistance service online in a simple way in by selecting the plan and then want to use the login information to log into the client area after the piament. English is not my primary language and I'd like to change the language of my plugin for french and ensure thats work with my theme I am lost thank you kindly guide me if anyone can.

http://www.techniciendirecte.com/register

Thanks

Jimmy V.