Summarize:

Tap the Settings app icon, which resembles a set of gears on a grey box. It's near the top of the Settings page. You'll find it near the bottom of the screen. It's near the bottom of the page. Doing so will open a screen similar to the Text Size menu found in the previous method. The switch will turn green {"smallUrl":"https:\/\/www.wikihow.com\/images\/1\/15\/Iphoneswitchonicon1.png","bigUrl":"\/images\/thumb\/1\/15\/Iphoneswitchonicon1.png\/46px-Iphoneswitchonicon1.png","smallWidth":460,"smallHeight":300,"bigWidth":"46","bigHeight":"30","licensing":"<div class=\"mw-parser-output\"><p>I edited this screenshot of an iPhone\n<\/p><p>License: <a rel=\"nofollow\" class=\"external text\" href=\"http:\/\/en.wikipedia.org\/wiki\/Fair_use\">Fair Use<\/a><br>\n<\/p><\/div>"}, and the slider below it will expand to show additional size options. Drag the slider to the right to see the largest text sizes possible. This will only apply to apps that enable Dynamic Type as well as allow the larger Accessibility sizes.
Open your iPhone's  Settings. Scroll down and tap  General. Tap Accessibility. Tap Larger Text. Tap the white "Larger Accessibility Sizes" switch . Enlarge your iPhone's text.