That will take you to a page that will allow you to add your picture. Mouse over the blank face and you will see a box appear that says, "Edit Profile Picture".
Once you are there, just follow the steps to get a photo of yourself from your computer. Keep in mind that the image will display very small, and in a square, so find a nice photo of your face. No one gets it right the first time so be prepared to go back and re-edit. Also avoid images of cartoons, or super-heroes, or your dog, or a random plant, or you with your truck, or groups of people etc. as it just looks ridiculous. This is Facebook. Show your face. You have a good face. Your friends want to see it!
Also, update it every once in a while. If you have been on Facebook for many years, you probably have changed a bit. But, please don't update it randomly. It's how your friends recognize you on Facebook, and if you change it often you just make it more difficult for your friends. Do it right, and leave it alone.
Use the same profile photo for Facebook, Linkedin, Google+, etc. If you're a professional, get a nice photo and hire a graphic designer like me, if necessary, to optimize the photo. It's your face to the world. If you're my cousin, I will do it for you for free if you need me to.
Now go show that wonderful face of yours!