The most obvious way to use social media is to advertise who you are and what you bring to the table.
Social media is great for this because there is so much content being created and distributed today, and social media is always the latest index to that material. By being the latest, your results will be the first on the list.
The second method is to use social media to locate people who can influence hiring decisions. You can seek them out, get to know them via social media and move that relationship offline. Once you do that, you're in the door for an interview!
But first you need to know which social media outlet does what and how you can use each one to up your chances of snagging a job.