Create/edit About us page
- Login to WordPress Admin
 - From WordPress Admin, click on Pages -> Add New

 - Enter title About Us and keep the body empty or write something identical and Publish the page.

 - Click on Appearance -> Menus and create a menu item for this About Us page

 - From the WordPress Admin, click on WT THEME_NAME Theme

 - Select Page - About Us outline

 - Click Assignments under Page - About Us outline
 - Enable About Us page you just crated under Pages section and Save Assignment

 - Click Layout under Page - About Us outline

 - Now scroll down, follow on-screen instructions and add/edit contents as you need.