To create a new page, go to WordPress Dashboard > Pages > Add New.
When creating a page you can add a title, content and Featured Image exactly the same way as when creating a post.
In addition, you have to choose the layout of the page in the "Page Attributes" box to the right. Click the drop-down menu entitled "Template" and select one of the options:
Default Template (with sidebar) - eg. > click <
Full-width Template (without sidebar) - eg. > click <