To create a new page or post, you can select the “+New” dropdown at the top navigation bar, and select the appropriate choice.
To edit a page, you can either click on the Posts or Pages menu item on the left side bar, then choose the item to edit. Or, you can be on a specific page or post, and click on the Edit Page at the top of the nav bar, or the Edit link at the bottom of the page.
Read on how to edit multiple posts or pages.