Open Settings
Tap Display & Brightness
Increase Display Zoom if available
Go to Settings
Tap Accessibility
Tap Display & Text Size
Turn on Bold Text if desired
Go to Settings
Tap Accessibility
Tap Zoom
Turn on Zoom to magnify the screen
Open the keyboard and use Zoom to make it appear larger
Rotate the iPhone to landscape mode for a bigger keyboard
Use a third-party keyboard app with larger keys
Enable one-handed keyboard mode only if you want a different layout, not a bigger keyboard