In the Settings app, tap Safari. Next to "Block Pop-ups", toggle the switch according to your preference.

1) Open the Settings app.

2) Tap Safari.

3) To prevent sites from displaying pop-up windows, slide the switch next to "Block Pop-ups" to the "on" position (to the right).

To allow sites to display pop-up windows, slide the switch next to "Block Pop-ups" to the "off" position (to the left).

Outcome

You have configured your pop-up blocker preferences in Safari on your iPhone or iPad.