[header] How to use four heading levels in apa style [title] Start with level 1 after your introduction : [step] Your paper always begins with an introduction followed by a level 1 heading for the sub-sections. Highlight the most important headings in your level 1. It is the primary topic related sub-section. 
[title] Format your level 1 heading : [step] The l1 heading must be aligned centrally, bold and should be in title case. A paragraph must follow the level 1 heading in your text.