How to secure network on iPad

This is potentially a big subject… but in practical terms for a domestic network is likely to be limited in what can be achieved.

What, specifically, are you trying to secure? Would this be your WiFi network, your wired network, your router - something else?

What devices will be accessing your network - and from where? With a better understanding of your network arrangement, both you and contributors here will be better equipped to understand and provide guidance appropriate for your need.

For WiFi networks, you’ll generally need to enable WPA3 or WPA2. For setting-up your WiFi network, consider this guidance from Apple:

Recommended settings for Wi-Fi routers and access points - Apple Support

For your network devices in general, ensure that your Router and other network devices are configured with a username and strong password - as these will help to protect their configuration from unauthorised changes or modification.