I can't even get Authy to install. I put in my mobile number (why?) and it tells me I haven't registered, with absolutely no indication of what to do now. http

I can't even get Authy to install. I put in my mobile number (why?) and it tells me I haven't registered, with absolutely no indication of what to do now. http://imgur.com/CGeeS.jpg http://imgur.com/CGeeS.jpg