If that's your laptop, then you've got an ExpressCard/54 slot on the left hand side near the front of the case. If you don't have that slot (about the width of a credit card, but thicker), then that's not your laptop.

If it is, all you do is slide the card in.

This might be the card for you, but don't take my word for it:

http://www.newegg.com/Product/Product.aspx?Item=N82E16839158047

I am the Doctor, and THIS... is my SPOON!