One doesn't. X3 Not yet anyway. More buttons are coming in short order! You can find more answers to more questions in the Site Update Survival Guide, which is in the Official Tutorials forum.
Follow along with the video below to see how to install our site as a web app on your home screen.
Note: This feature currently requires accessing the site using the built-in Safari browser.
Btw almighty bbcode goddess. How does one spoiler in this new fangled site?