How do you send in a TV show script to a Television Company?

Make sure you keep proof and copies and send it registered/certified mail
Are you sure you are wanting to send it to the TV company and not Hollywood producers?

Yes, first you want to copyright it in the US, so you own the rights to it. But you will have to send it to the producers who will decide if they want to buy it. Or if not they may wish to offer you a job as a writter for them if they see talent but don't like that script. Also many will not accept scripts unless it comes from a UNION writer, since many TV productions are closed to non union writers.
But it is the producers, and often people even travel to them and try to sale the idea to them in person.