Settings
More Settings
Tethering and portable hotspot
Switch on "portable WiFi hotspot"
Allowed devices
Choose your ipad
Now connect to WiFi network = your mobile phone on your ipad
Edit: you may have to try to access your phone hotspot first from your ipad and then allow access in your phone settings. I dont remember, it is a while ago that I had set up my devices.
This is the answer I was going to give too. I have my phone settings so I can ether the iPad to the phone's internet connection. I don't have unlimited download on my phone though so am careful of how long I do it for.