how do I connect my hp to apple tv

Hello,

What exactly are you wanting go accomplish? Your HP computer runs Windows which does not natively support Apple's AirPlay technology, which is what allows a device to share its content to an Apple TV. The exception is that by using iTunes you can AirPlay iTunes music, tv shows, and movies to your Apple TV.

How to AirPlay audio - Apple Support

There are windows softwares that mimic the AirPlay protocol (somewhat). Plenty to find on the web about that.

Needless to say, it is not officially supported by Apple.