Unless you have a one page website you are going to want to add some pages and posts.
The difference between pages and posts are that pages are static and usually feature in your menu bar whilst posts are automatically added to your blog feed on your blog page and are normal added on a frequent basis.
This video goes through how to add a page and a post and shows you how to add a featured image (which will show up when you share on social media when you share the link – this applies for both pages and posts)