Nothing like the practice can make you understand the underlying designing work: that's why you can download the KiCAD files from HERE.
The project is released under the Creative Commons Attribution - Share Alike 3.0 license.
[You are free in all but the use of name Serialino: you have to ask the permission]
The zip contains both schematic and pcb files, plus the net and the compare files.
[And you'll find two files, 8pinheader.emp and 8pinheader.mod, used for the headers. You just need this last one, by copying it into the modules folder of KiCAD installation folder]
Furthermore, a png image taken from the 3D viewer, which you can launch from the PCBNew application of KiCAD.
3D Display is a good tool to have an idea of the final board's aspect.
We strongly suggest you to play with the pcb file: the strength to improve will be very formative.
But as always, do it for fun.
The following video quickly reports what we've just described.
Next time we'll see Serialino running, even with other boards onto it.