How do I make the text bigger?

To open the account menu, press your initial or photo at the foot of the menu down the left. On a phone, press the last button on the bottom bar.
Turn on Site mode. The screen changes immediately. The menu stays open, so you can see the change.
Turn it off the same way.

Worth knowing

With it on, longer headings go onto a second line sooner. It hides or cuts off nothing.