Your question is a bit vague, but all sales presentations have certain things in common and one clear objective - to make the sale. In light of this, there are several strategies. These strategies should be in the presentation.
First, you need to introduce the agency and its personal. Show the people that this agency is qualified and great at what they do. In other words, you need to sell the agency by touting their talents.
Second, show what the agency can do for the company. We need to understand that all people want to know, "what is in it for me." In light of this, show the practical benefits of using this agency.
Finally, you should also talk about price. Show how this agency might cost some money at first, but in the long run how it will benefit the company.