Well, it seems the provided context is about as helpful as a screen door on a submarine, offering only YouTube's legal footer and a link to Reddit. So, let's disregard that and tackle the real problem based on hard-won experience.
Ah, the great sofa cover wrestle. A domestic trial that has tested the patience and strained the biceps of many a brave soul. You've washed them, they're clean, they smell fantastic... but now they seem to have shrunk two sizes and developed a personal vendetta against your couch cushions. Fear not.
Your primary foe is the cushion itself. The secret weapon here is what I call the "taco" method. Fold that foam cushion in half longways, like you're making the world's most uncomfortable taco. While holding it in this compressed state of submission, begin sliding it into the cover. Get it as far in as you can before carefully, and I mean carefully, letting it expand back into shape. You’ll then need to shimmy and adjust the corners until they align, which is its own special kind of joy.
For the main frame cover, think of it like dressing a very large, uncooperative toddler. Find a clear starting point, like a corner or an arm, and align it perfectly. Drape the rest of the fabric over the sofa's body. Now comes the sacred art of tucking. Use your hands, a wooden spoon, or even a ruler to shove the excess fabric deep into the crevices where the back and arms meet the seats. This is what separates a tidy sofa from a sad, baggy mess. Once everything is tucked and smooth, fasten any zippers or Velcro with the triumphant finality you so rightly deserve. If all else fails, a second person can turn this Herculean effort into a mildly strenuous team-building exercise.
