To create a subsite, works similarly as to create a second language.
In the download you will find a folder "2site", that you can copy, rename and upload to the installation directory of CMSimple.
Unlike a second language, the folder name of a subsite should have more than 2 characters (example: Subsite01).
Now you need to set the necessary read and write permissions for a few folders and files.
"subsite" is for example only.
Folders: chmod 777
Files: chmod 666
Now your subsite should work.