How can I sell myself to a business?

I apologize if this isn't the correct forum to be posting this question in, but I need some advice. I am in the interview process for a company that produces large fabric tents. I am trying to get the role of Marketing Assistant, and today they asked me if I could develop a marketing campaign selling myself to their company. I have until this coming Monday (9/21). I have never created my own marketing campaign before, but feel very confident I could do so if given some advice, and a nudge in the right direction.

What the position entails:

• Managing the companies social media presence
• Creating graphics for marketing campaigns
• Writing content for marketing campaigns

What they want:

• Word document selling myself to the company.
• Focused more on bullet points, my cost, time commitment, etc.

What I am thinking:

• Some sort of catch phrase: "Leave your doubts out in the cold." etc
• Small graphics around the page, possibly a graph of some kind with my "ROI".

If anyone is interested the company website is here---> www.aks.com
Thank you for any advice you are willing to share with me.

Hi Sean,

I think they'll be most interested in RESULTS. Specifically what YOU can achieve for THEM, as well as WHY you would do that - and HOW. Sell yourself (and your skills/commitment) to them in the same way you would sell a Kirby vacuum cleaner. ;-) They basically want to see if you can sell THEM to their target market, and your pitch is how they will determine that.

I hope this went well, Sean. I wouldn't feel very comfortable if I had to promote myself this way.