How do I add keywords?

So I've done extensive keyword research, and I now have a list of niche keywords which I have been targeting mainly through blog posts and products. Ontop of this, I have also been building quality back links around these keywords.

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However using Ahrefs, I can see my site isn't ranking for any of these keywords, despite focussing on them for a little while now - could anyone provide any insight of why this is?

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Is it just a case of persistence?

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Thanks.