I never had the chance of getting Dogmeat in the main story and after I beat the game I learned about him on the internet. I am wondering if there is a way to get Dogmeat after the main story if you never had him before the ending.

If you've never gone to his location, then yes. If you have and he is dead, u need to pick a perk.

I got the Puppies! Perk. All I have to do is go to the scrapyard?

Yup!