The first thing you should do is to get enroll for Social Security.
You need a Social Security number to get a job, collect Social Security benefits and receive some other government services. But you don't often need to show your Social Security card. Do not carry your card with you. Keep it in a safe place with your other important papers. [Source – SSA]
You only need I-94 and your original Passport, which will be a proof of your Age and your Identity, which is required to file an application for Social Security Number/Card.
You can locate the SSA offices or affiliates that are closest to you from - https://secure.ssa.gov/ICON/main.jsp
When you reach the relevant SSA office, you will have to fill an application form called, Form SS-5, see snapshot below:
Officials will ask some questions mostly related to your Age and/or Identity i.e. your Passport. If every thing is ok, then they will inform you about the time when you can expect the Social Security Card in your Mail.
A Social Security Card looks like:
Valid for work only with DHS Authorization.