To create the needed files for manufacturing the board load the project in KiCad. Then open Pcbnew and click file->plot to create the Gerber files. In the plot dialog select the following settings:

Click on "plot" to create all needed Gerber file. Now click on "Generate Drill File" to open the next dialog window. Now you have to select the following settings:

Click on "Drill File" to create the Exellon drill file. To group all files together it's a good idea to create an empty directory and select it in the "Output directory" field for both dialog windows.

There is a little bug in KiCad where one of the created Gerber files has a false extension. To fix this you should rename the file with the ending *.gm1 to *.gml (One to lower case L).

To be sure your files are correct you can verify them in the next step.

To verify your exported files in Gerbview, which is also part of KiCad, just start Gerbview and load the following Gerber files:

argon_disco_adapter-B.Cu.gbl
argon_disco_adapter-B.Mask.gbs
argon_disco_adapter-B.SilkS.gbo
argon_disco_adapter-Edge.Cuts.gml
argon_disco_adapter-F.Cu.gtl
argon_disco_adapter-F.Mask.gts
argon_disco_adapter-F.SilkS.gto

The colors are not relevant but the origin of the board should be at the upper left corner. This is shown with the blue grid lines.

Now you have all files you need to let the board be created by any pcb manufacturer. Just zip all files and send them in.