I have iOS 10.3.3 on my iPad. How can I install only iOS 13 on my iPad so I can watch spectrum tv on my iPad. Thank you

If your iPad has iOS 10.3.3 it is almost certainly an iPad 4th generation and if so, that is the latest iOS that can be installed on it. It cannot be upgraded to iOS 13.

If you are unsure of the model, see: Identify your iPad model - Apple Support

If your iPad is currently running, or cannot be updated beyond iOS 10.3.3/4, then have an iPad4.

Update support for iPad4 ended September 2017. The final iOS releases for this model were iOS 10.3.3 (WiFi Only models) and iOS 10.3.4 (WiFi & Cellular). iPad4 cannot be updated to any later major version of iOS as it lacks the minimum hardware requirements needed to run more recent versions. The 32-bit platform upon which the iPad4 is based is effectively obsolete.

Most App Developers have dropped support for older devices and iOS versions preceding iOS11/12/13 - and have withdrawn older versions of their Apps from the Apple App Store. Withdrawal of Apps supporting older models of iPad is making their utility and usefulness significantly more limited. Once compatible versions Apps are withdrawn, you’ll not be able (re)download or (re)install them.

If Apps that you need to use now have higher minimum iOS-version requirements, your only option is to replace your iPad with newer model. Of current models, even the entry-level iPad7 supports current iPadOS 13.x and soon to be released iPadOS14 - and has hardware specifications and capabilities that vastly outperform your old iPad4.

I hope this information is helpful - if only in clearly stating the limitations of your iPad4 and your available options.