By navigating to CRM-->Contacts-->Settings, you have the option to adjust the visibility and order (via drag-n-drop) of the default fields of the "Add Contact" form. Additionally, you can control the visibility, order (via drag-n-drop), and requirement status of any Custom Fields you have created for the same "Add Contact" form. To adjust visibility (for default and custom fields) or requirement status (for custom fields), simply check or uncheck the box next to the desired field. To adjust the order of the fields, simply click and hold the desired field row, and drag the row up or down to move it.