There is a quick start guide here;
which has a link to an image file you can download with everything already configured.
In saying that, it is sometimes best to do it manually so you can get an idea of how it works.
Regarding the files not accepting the changes, you mustn't be doing something right. How are you saving or closing Nano? I do "Ctrl-X" to exit and then it will ask if I want to save changes."y" to save changes.
Or, you can hit "F3" to save without closing Nano.
Your Pi and PiScreen should work of a battery pack.
The attached image shows PiScreen sitting on top of a B+
Mark --OzzMaker.com --