The Screen Options allow you to choose which items you can use to add to a menu. Certain items, like Posts are hidden by default. The Screen Options are located in the top right corner of your WordPress Dashboard.
Step 1 : Locate the pane entitled Pages and within this pane, select the View All link to bring up a list of all the currently published Pages on your site.
Step 2 : Select the Pages that you want to add by clicking the checkbox next to each Page’s title. Click the Add to Menu button located at the bottom of this pane to add your selection(s) to the menu that you created in the previous step.
Step 3 : Click the Save Menu button once you’ve added all the menu items you want.