Open Safari and go to Preferences. Under the Advanced tab, at the bottom, you’ll see “Show Develop menu in menu bar”. Make sure that is checked like in the image below.
Once that is checked, you’ll see a new menu bar item named “Develop” between “Bookmarks” and “Window” in Safari’s menu. Under the Develop menu, select “Simulator” and then select the site you want to debug. A new window with the developer tools will then pop up:
