The 35mm macro lens I've been using with the K-50 creates lovely bokeh.
Bokeh can be more tricky than you might think to get right. The technique involves throwing the background of your image out of focus, using a large aperture (small number) to create circles of light on the blurry background.
While experimenting with this technique I discovered that it only really works well if there is a light source in the background, for example fairy lights, light coming through the dappled treetops in the woods or something shiny, like the fireplace in my shot here.
You also need to consider the distance between the object and the background and the object and the camera, to get the desired effect. Have the object too close to the background and it will blur, or the background won't blur enough to create bokeh. Have the object too close to the camera, and again you might struggle to get the look you want. I found that having a smaller distance from the object to the camera and a larger distance between the object and the background worked well as a basic start point.
Altering the aperture makes a big difference to the area that's in focus. The max aperture on the 35mm lens is f/2.8, and this creates lovely bokeh, but this makes keeping the desired subject in focus quite difficult, as the slightest movement will throw it back out of focus as there is quite a narrow plane of focus at this aperture. Using a higher aperture number, say f/4 or f/6, will give you more room for movement.
The best way to get the focus just right is to use a tripod, and use manual focus. This allows you to make tiny corrections, and focus on what you want, rather then what the camera wants. This is made really easy on the Pentax K-50, there is a switch on the side of the camera to apply manual focus and the 35mm macro lens is really well damped for making fine adjustments.