Welcome to the Q&A Forum

Let me understand your question. Your website is indexed but when you check on the search engine your website won't appear on the search result, right?

So here is my advice first you need to check your search console.

Search Console > Search Analytics > Download the report, then you will have a clear idea of your keywords ranked, anchor text, position, CTR and so on.

Organize your keywords by themes and then start to optimize your site with those themes/keywords.

So where is the question?

If you need something easy I will recommend you

• https://moz.com/explorer
  the other option SEOquake for Chrome
  https://chrome.google.com/webstore/detail/seoquake/akdgnmcogleenhbclghghlkkdndkjdjc?hl=enBoth will give you a clear idea of the complexity of keyword

For me Yoast is the best, I'm using the premium version for my blogs

Rankie - Wordpress Rank Tracker Plugin (good for keyword tracking)

Rich Snippets WordPress Plugin (good for structured content)