The first thing to think about when feeding your dog is: is this food actually nutritious for canines? One of the trusted sources for you to look at is AAFCO — the establish the regulations and standards around balanced pet foods.
The second thing you'll need to check is: is this food right for my dog? Each dog has its own needs depending on allergies, injuries and illness. A certified veterinary nutritionist could be a great person to consult with to find the right food plan for your dog — visiting at least once per year is what we'd recommend.
And finally: how much should you feed them? Again, this is often tailored to a dog's needs depending on how active they are. But the general guidance is anywhere between 1.5-3% of their bodyweight on a daily basis. For new dogs in your home, it's a great idea to weight them regularly to understand how their weight fluctuates — this will help you understand your dog's needs more clearly.