An agent can help get your script into the right hands. Agents will list on their website specific instructions on how to submit your writing. The Writer's Guild of America is a reputable resource for finding agencies.  Almost all agents will require a query letter. This is a letter in which you sell your writing and yourself to the agent. Some require a specific format so check their website. All are looking for something that stands out so make sure your letter highlights the best parts of you and your writing. An agent shouldn't charge upfront to represent you. Most agents' fees are 10-12 percent after they broker your deal. If an agent asks you to pay a fee just for representation, move on to another agency. You can look up information online about how to submit your script to them as they have specific, individual instructions. Many do not accept scripts, depending on legal issues with their current shows. The ones that will accept them usually have instructions on their company site for submitting episode manuscripts. Becoming a writer's or producer's assistant is an excellent way to get your foot in the door of TV writing. You will not make much money, but you will be exposed to a TV show from the off camera point of view. This will allow you to read scripts, see how writers and producers work in real time, and make numerous connections within the industry. Check out the job opportunities section on the home page of the production company you are interested in joining. Search online for workshops, conventions, or meet and greets in your field. Join media groups online and follow them on social media. The more connections you make, the better your chance of getting a foot in the door.
Get an agent. Send your script to TV showrunners and executive producers. Apply for a job as an assistant. Network as often as possible.