To add additional menu links and content pages to your store, users on the old admin would go to Settings ->Design ->Site Content
Now, the same area can be found by going to Content ->Site Content
As before, there are two sections for Site Content; Menu Links and Extra Pages. However, rather than being displayed top to bottom, they are now displayed laterally; with Menu Links on the left and Extra Pages on the right.
To add either, simply click on the “+Add” button located at the top of each section and create the necessary content. The same functionality as before exists.