Easy rewriting outline.
Short introduction. It should just be a paragraph. State the argument in the introduction and highlights what you are going to discuss in the body in sequential manner.
Each paragraph must be clear and separate from the previous one.
The following must appear:
-Brief discussion of what conventional or traditional security is
– its challenges or limitations or criticism of traditional security. At least 4-5 points
-How HS challenges the notion of conventional security.  Give key tenets of HS.
– Why HS is better framework for analysis of security.
-Short fall or criticism of HS. Give the critical short fall.
Add more credible evidence.
I.e. HS as been criticized on the following grounds:
    Lack of consensual about its definition or what it seeks to address.
    As policy agenda
    Its universalism is term as project of western values and principles.
    And two more points.

-Conclusion. You should give a solid conclusion. Dont introduce new idea.
Do not write in heading and sub headings. Remember this is an argumentative essay. This structure is just guideline of what is expected of you.