Click the Share button
in the toolbar or choose File > Share, then choose how to share the webpage. When you email a page, Mail lets you choose whether to send it as a webpage, PDF, link, or, if Safari detects an article on the page, a Reader article. For more information, see Send a webpage shared from Safari.
You can choose which items appear in the Share menu by using the Extensions pane of System Preferences. For instructions, see Share on Twitter, Facebook, LinkedIn, and more.