To make 3d files (.stl) you can either download some from a site like www.thingiverse.com or make your own in TinkerCad.

When you have your stl files you need to use a slicer program to slice it into layers and make gcode.

Here is Slic3r, the file also includes a .ini file which you can load from slic3r to set all the settings for your printer.

When you've got your gcode file you need to send it to your printer, we'll use Printrun Mac or else use Printrun Windows.

If Prinrun has an error and asks for Java Runtime or JRE, download and install this one for Mac or this one for Windows.