First, you need to select the Close-Up Mode at the camera Mode Dial. You might found your Dial looks different, but I'm sure you can find the flower icon ( In red circle) at the Dial :)
So, what does Close-Up Mode do? Let's begin. These are the setting for my camera, but it will be about the same as yours as well. Do not worry ^^
Aperture = Auto
Shutter Speed = Auto
Exposure = Not Available
ISO Speed = Auto
Picture Style = Standard
White Balance = Auto
AF Mode = One Shot
AF Point Selection = Auto
Drive Mode = Single
Metering Mode = Evaluative
Built-in Flash = Auto
Do you remember the chapters "How to Use Portrait Mode" and "Controlling the Depth of Field"? In Close-Up Mode, you can't control the Aperture because it is in Auto. But, the camera is designed to use lower f-number Aperture in order to narrow the depth of field and make the background blur.
There are something similar between Portrait Mode and Close-Up Mode because both of these Modes are using a lower f-number to blur the background. So what is the different between these 2 Modes?
Portrait Mode is designed for tuning the skin's tones in order to have a healthier, lighter and softer result. Of course, Portrait Mode colour control will not only target the subject, it target Everything in the picture. The colour of Portrait Mode will be lighter most of the time, compare with Close-Up Mode. Therefore, I would say the main difference between these 2 Modes is the Colour.
Some model of compact digital camera will automatically switch into Close-Up Mode if you put your camera near to the target, even the target is a human being. The digital camera does not know whether it is a skin or a flower, insect, food and etc. The distance of focus determine the Mode as well.
By the way, I do prefer to Zoom In to the target instead of getting close to it. It is because some Lens have a minimum distance and if you get too close, you will not able to focus. Also, you might disturb the target (animal, insect, or something holding on someone's hand), I believe that is not a good move. :)