How to store a favourite pet for a logged in user?

Using React and Express, how can I store a favourite pet for a logged in user? Currently pulling the pets from an API and then using PostgreSQL for the DB

const favPetDetails = {
    id,
    name,
    media,
    breeds,
    location,
    distance,
    sort,
    url,
    tags,
    type,
    gender,
    contact,
    environment,
    attributes,
  };
  const addFavouritePet = (Pet) => {
    const newFavList = [...favourites, Pet];
    setFavourites(newFavList);
  };


 <button onClick={() => addFavouritePet(favPetDetails)} </button>