Take a deep breath. Now, don’t worry. Just think “outline form” only with different formatting.
You may not put headings into your work but you probably could. But if you know outline form you know that you have a main heading, with subheads under it, and then possibly sub-subheadings under that. So your main heading for a given section is “level 1,” any subheadings under that main one are “level 2” and any subheads under those are “level 3.”
Now, your 1st-level heading, which might have a roman numeral if you use those, is centered, bold, using up-style capitalization.
2nd level headings are flush left, bold, up-style.
3rd level are indented, bold, with only the first word capitalized. Then unbold and run your first paragraph in (that is, don’t start a new paragraph, continue as if the heading was the beginning of your first paragraph, which it is).
4th level, if you get that far, is bold italic, indented the same as 3rd level.
5th level, if you get that far, is italic, indented the same as 3rd level.
(I have seen people use bold ital for 3rd level and bold for 4th level. If you’v been given some guidelines, follow them.)
So, to recap, if you have an outline like this:
I.
A.
1.
a.
b.
2.
B.
I = first level
A = 2nd level
- = 3rd level
a. = 4th level
i. = 5th level
I should say, if you only have one of a given subhead, then you don’t actually need a subhead for that section, and the first subhead is always the next level–you don’t jump from A. to a.
Also, as an editor I get lots of papers that have the headings numbered. Our house style is not to use numbers. I think APA style for publication is the same. However, if you want to make sure your headings are corresponding to your outline, keep the numbers until your last edit.
PS: Heading I is not “Introduction” and don’t even write the word over your introduction, likewise your conclusion. Unless, of course, your prof wants that.
ETA: I don’t know what happened to the spaces in my sample outline form, and I don’t know how to indent in vb!