Have your agent submit the listing to the listing office. I always request to be able to present the offer myself to the sellers. But, the agent should have someone covering their listings.
Coldwell Banker Triad
With that being said, don't make an offer directly to a listing agent. You need to hire a buyer's agent - someone to look out for your best interests in the homebuying process. It costs you nothing - they typically are paid by the seller. The listing agent represents the seller and is looking out for the best interests of their client - they want the highest and best possible price.
A buyer's agent will help you with market value, negotiations and the maze of paperwork needed to get through the home buying process.