Custom Share, Login Button for Facebook SDK iOS

Im sharing image to Facebook to using Facebook SDK. problem is i dont know how to change those buttons to custom buttons. ex: if i trigger button then it shares with facebook.

here my code. this is the one Facebook give as default

let button : FBSDKShareButton = FBSDKShareButton()
        button.shareContent = content

        self.view.addSubview(button) // how can i trigger with my button
        button.center = self.view.center // i dont want this in center either