How do I apply food I buy to a horse? 

e.g. I bought 5 servings of food but none of my horses have any more on their “Feed left” than they did before. 

Daily 

Okay if I understand right really what I should be doing daily is making sure my horses have food / vet / etc and enter them into shows to collect points and that’s the full game? Am I missing out on something (beyond breeding which you wait to do until they’re older I know) 

Also how do I see the results from shows my horses have been in? 

If you have an upgraded account, you buy stalls and food from the store. On each animal's page, scroll down to where it says about boarding at home, on the left. Go to the top of your page and click Home then click Stable. Then you can add food!
If you're a basic, you do the same as above, but there's a dropdown menu with players' names who have stables. Select one then pay boarding and the owner will feed. Might want to drop them a message to let them know your animals are there. Some feed in bulk!

The only thing you need to do daily is train. I'm not sure of the times between animals needing vetted and farriered, but it'll come up on your animals' pages.

To see results, go to an animal's page and click Show Results and you'll see all shows still to run plus how many places you have.

beck read this

https://horsephenomena.com/upgrade_help.php#boarding

Looks like Kuwait and Nyx have you covered on the boarding aspect!

The largest part of HP is training your animals, but there is a lot more to do! Some people do project animals, participate in clubs, train for other people, do art or layouts, participate in breed embassies, do the contests/events offered by the staff, and participate in chat and the forums! We also have a mini game to earn HPD.

If you need a place to board, my stable/kennel is always open and always free. Just make sure you pay the $0 board and I will add feed to them. :)