Update IOS

You cannot use personal hotspot on the device. You iPad MUST be connected to a reliable and possibly fast Wifi Network with Internet access. Then tap on "15 Upgrade to iPadOS 15" at the bottom.

Regards

Giulio

You should note that for your iPad to install an available update, its battery must be charged to at least 50% capacity - and/or be connected to its Power Adapter. Similarly, the iPad can only be updated over a standard WiFi connection - or be updated by a PC or Mac using iTunes or Finder - over a USB connection.

Update over a Cellular hotspot is only possible over a 5G Cellular connection.