How do I link my cable services to my Apple tv

Use your pay TV or cable provider with Apple TV - Apple Support

The Spectrum content would be available in the Spectrum TV app.

Certain networks with their own separate app that require a TV provider subscription (ABC, NBC, etc.), may also be available through your TV provider credentials. You may set your TV provider in Settings﹥Accounts to automatically sign in for ‘all’ of those. However, it should be automatic for Spectrum TV in combination with Spectrum Internet (“Zero Sign-on”).