Agents don't publish; they sell stories
to publishers in return for a percentage of advances and royalties paid to the writers. To land an agent, you write a query letter. (There are other ways, like being really famous.)
A good on-line source for agent stuff--and query writing, too--is
AgentQuery. Also, you can verify an agent's bona fides at
Writer Beware and
Preditors & Editors. Refer to each agent's website for submission instructions; they are not all the same.
Query widely and simultaneously. Avoid exclusives.
Don't pay anyone to represent, edit, or publish your work.
Hope this helps. Good luck.