How do I show battery life percentage on my phone

You can only swipe down from the Home screen to show your Control Center and in the upper right corner is the battery percentage. It no long shows on the Home Screen for iPhone 11 and some of the others like iPhone XS/XR.

Go to settings- battery - toggle battery percentage

In addition (if you find it more comfortable), you can add a widget about battery.

Regards

Giulio