Select and buy a bearing according to your application. There is various alternatives at ebay. Design a housing with a CAD program with you know. While designing a housing be careful about bore diameter of housing. Since the printed product shrinks %5 to %10 percent (I believe it depends on your cooling rate, plastic material and density) you may need to design hole bigger according to desired fit type.
Before the final product, you may print a basic sample which simulates inside and outside diameter of your housing. Since my bearing outside dia is 16mm and I wanted a press-fit, I designed my housing bore dia at 16mm. After the print I measured it and it was 15.4- 15.5. I easily mounted bearing with a clamp or pliers. (Nut housing is shown as an extra example) I strongly recommend clamp since uniformly distributed pressure on the bearing won't deform the plastic housing. If the fit is loose you may use loctite or if the fit is too tight you may use sandpaper.
After you decided your bore dia, print your final design.
My design includes two attachment holes, so I can attach it anywhere with nut and bolt but also you can drill a thread and eliminate the need for nut. It is pretty easy, you do not need a special tool since the material is plastic. Mount the part to a clamp and try to tighten bolt with a downward force. After it is engaged, rotate bolt CW and CCW several times.
Here is my final assemblies. You can also make housing with shoulder to withstand more thrust load.