How to create a
child page of another page
Pages are referred to as parent and child pages (in drop down menu). This tutorial will show you make a child page in WordPress.
Again with wordpress this can be achieved in different ways.
Open Services page add your content and in Page Attributes add it as a child of your WordPress Development Page.
This can easily be done in Menu >> Click Appearance >> hover over WordPress Development and drag and drop the page slightly to the right(hierarchy or visually a Dropdown), into place under Services. Save your Menu.