There's not much to say. The plugin includes txt-files, containing html source code, into a CMSimple page. The txt-files are stored in a subdirectory of the CMSimpleRoot, in a folder userfiles/co_author/.
In the plugin call you have to tell the plugin the subdirectory of the CMSimpleRoot, where the folder userfiles/co_author/ is located, and the name of the txt file.
The exactly syntax of the plugin call is explained in the help file (help.htm) of the plugin.
The plugin is installed just like any other plugin too. Just unzip the download and upload the files and folders of the folder "plugins" in the "plugins" folder of your installation.
There are no problems with writing permissions for files and folders, there are no data files, language files or config files.