how can I use my iPhone to link my ipad to inte...

Connect iPad to internet through iPhone

If your carrier supports it, and your cellular iPhone service account with them is set up to allow it, then you can use hotspot tethering - Share your Internet connection with Personal Hotspot - Apple Support to share your iphones cellular internet connection with other devices.

If hotspot does not appear as an option on your iphone then contact your carrier about adding it to your account.