Now that you've decided that you want to build the idea you're imagining, you need learn how to use 3D design software.  This software can be extremely expensive and only affordable by big companies, but luckily, there are free software available that anyone can download and use.

The 3D printers Fort Erie Public Library require wire-frame model designs with the STL file extension.  The complementary software for these printers is Autodesk's Tinkercad, which is a free online 3D software.  Tinkercad allows you to also share your designs on their onsite gallery as well as on the Thingiverse web site.

As with pretty much everything, if you need to learn something, there are video tutorials.  Having had a chance to try both Tinkercad and FreeCAD, I find that I prefer using FreeCAD.  FreeCAD designs need to be exported to the STL format before they can be 3D printed and this is a very straightforward process.  However, Tinkercad is simpler and easier to learn.  You can also just download an existing design if it serves your purpose but feel free to reward the designer with a donation for his efforts.

Visit these sites to learn how to use each.

Tinkercad

Tinkercad - Basic Skills
YouTube - Autodesk Tinkercad Tutorials
YouTube - Inventor Studios

FreeCAD

FreeCAD Wiki Tutorials
YouTube - Learn FreeCAD Channel
YouTube - MarthamEngineering<