To get to the Page SEO click on Website Settings -> Page SEO
To get to the page SEO of a specific page on your site -> go to Pages -> go on top of the Page -> click on the 3 dots -> Show Settings
It will open up the Page SEO settings where you can add:
Meta Title - this is the title that outlines what the page is about. It is the page used by Google to show in the results page. The orange tracker shows the optimal size of the Meta Title. Make sure you have a compeplling sentece with keywords that are important for the page visibility.
Meta Description - brief explanation of the page of around 300 symbols. Make sure you also include keywords in the description and to be a nice compelling text to make people click on the page when it shows in Google.
Add to Sitemap - that adds or removes the page from the Sitemap.xml that helps Search Engines to index (find) your page. If the page is still in progress make sure that it is removed from the Sitemap.
Share Image - used for social media sharing of the page.