Usually, each page within your site should focus on a narrow sub-set of keywords, with one dominant keyword. For example, let’s say you are creating a site about "golden retriever puppies". If your research tells you that term gets good traffic, then that should be your primary keyword for your home page.
So let's say one of your secondary pages is about "buying a golden retriever puppy". So "buying a golden retriever puppy" should be your primary keyword for that specific page. Your page should also contain other closely related keywords such as "golden retriever puppy habits", "golden retriever puppy behavior", "golden retriever puppy pricing", and so on.
Resources:
On Page SEO - Creating an Optimized Page
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