Lets explore in depth the option of the Yoast SEO Metabox that you found at the bottom or the editor. The box will provide four tabs with different features. the first one is SEO tab.

Under the SEO tab you will have the section to enter your "Focus keyphrase"

Focus keyphrase
Help on choosing the perfect focus keyphrase
(Opens in a new browser tab)

"Google Preview" this section give you the options to preview your post or page on search results. also you have the option to display in mobile or desktop.

"SEO Analysis" it will display the analysis of page or post and the areas that need to be revised

"Advance Section" you can decide whether you
want search engines to include your post in the search results.


Allow search engines to show this Page in search results?
Learn more about the no-index setting on our help page.
(Opens in a new browser tab)
Yes (current default for Pages)
No
Yes

Readability Tab: , there is the analysis of, for
example, the length of the paragraphs, subheadings distribution, or the
use of passive voice. It also includes the readability score of your text.


Schema Tab: allows you to add a schema to your website helps Google understand what it’s about. This, in turn, helps Google serve the best result to their users.

This helps search engines understand your website and your content. You can change some of your settings for this page below.

Last tab is the social tab. where you can preview (premium feature) how your post or page will look of facebook or twitter. You can input the values but it will not show you the preview since this 

You can also find the same features of the Yoast SEO metabox on the sidebar of the post and pages.

Yoast SEO will give you pre publish check for a last minute revision if you are not happy.

after you click "Publish" you will see the SEO on the right panel with an analysis of the post or page.

We've analyzed your post. There is still room for improvement!

After you publish, the plugin will have a section to share post or page to social media

Facebook
(Opens in a new browser tab)
Twitter
(Opens in a new browser tab)

Yoast SEO in depth