How do I install Cellular on this iPad Disabled Military Veteran

First, be aware that there are two models of the iPad -- Wi-Fi only and Wi-Fi + Cellular.

If you have the model that supports cellular, see the information in iPad + Cellular - Apple and Set up cellular data service on your Wi-Fi + Cellular model iPad - Apple Support

You cannot add cellular capabilities to a WiFi Only model of iPad.

It is impossible to upgrade the internal hardware (e.g., RAM, CPU, internal storage WiFi or Cellular radios) of your iPad - as these are fixed during manufacture; what you have is fixed for the life of your device. 

If you have a WiFi+Cellular model of iPad, you can activate cellular capabilities by adding an appropriate Cellular service plan:

Set up cellular data service on your Wi-Fi + Cellular model iPad - Apple Support

Whilst a WiFi Only iPad cannot be transformed into a WiFi+Cellular model, as an alternative, you can use the hotspot feature of a mobile phone - or a Cellular Broadband Router (often known as a MiFi Router) - to access Cellular networks.

How to set up a Personal Hotspot on your iPhone or iPad – Apple Support

Chopyakj wrote:

How do I install Cellular on this iPad Military Veteran 8th Generation iPad

If purchased a cellular + wifi ipad you will need to contact your cellular data company to get it activated.

If you purchased a wifi only ipad you can't install cellular data.

Sorry, your question isn’t clear.

You can’t “install cellular”.

Are you asking how to activate cellular service? Are you asking how to reset a device that is disabled?