Just to start with, I'd set the camera to aperture priority mode ( I use Pentax so not sure what this is on the Nikon setting dial - probably A or AV), and set it at F11. Put the camera on a tripod with a remote release (quite cheap usually) at the 55mm end of the lens. Experimentation will show the best distance etc, and the setting can be tweaked a bit. No substitute for practice!

Gerry, the theory is the same for all SLR cameras, you need to have the aperture closed down as small as you can - f29 - in order to get the depth of field you want. Because that's so small you needa fairly long exposure, but exactly how long will depend on various factors: how bright your lighting is, the colour of your subject and background, etc. And because the exposure is fairly long, you need to keep the camera very still, so ideally a tripod; instead ofa remote shutter release you could use the self timer or just be careful when pressing it.
To access the manual mode on a Nikon (all cameras?) Turn that dial on the top to M. Turning the black knob with your thumb will make the exposure longer or shorter and this is shown on the graphic display; hold the little +/- button at the same time as turning that thumb knob will adjust the aperture (f stop).
So witha white background, a daylight type task lamp pointing at the model, cameraabout 7 inches from subject, on a tripod, aperture right down, I often use an exposure time of about half to quarter of a second - shown on the display as 4 or 2 - only when it is over 1second you'll see the " displayed.
If photo is too dark increase the exposure time, and vice versa. You also need to work out how close you can get; try the autofocus and see how closer you can get with it allowing you to shoot; if too close it will kind of lock the shutter. On manual focus you can probably get closer and have a bit more control, but the autofocus is very convenient.
I agree, practice is what is needed to get the hang of it, but keep the aperture down small, have plenty of light and keep the camera still for the exposure necessary, andyou should get something decent eventually.

What might also help is using a macro lens that can be screwed in at the front of the lens acting like enhancement glasses. Not as good as a true macro but it helps and is cheap. Nice add on to the 18-55 on my Canon

As already said a tripod is extremly helpful. Does not have to be a costly one since you will use it indoors. Cable based remote is useful as well, does not have to be the more costlx radio type. The automatic release can be used as an alternative since the msin idea is to remove vibration.

Good lighting is also helpful and a lightbox can be useful. This can be as simple as a cardboard box with cut outs at the top and sides covered with transparent paper. Shine the lighs through it to soften it and get less shadows. The white or generally unicolored background should be run in a slight half-c curve from the top to prevent a fold showing.