SUBFOLDERS

TURBOPY is quite flexible when it comes to paths. By default it expects an installation directly under the domain like http://localhost/. The default directory structure is like this:

tPy_site <- the installation folder
  ...
  pub
 <- the public folder with index.php, tPy.php, images and so on. This is also the document root for the server.

The document root for the server should usually point to tPy_site/pub/. If you want to install the site in tPy_site/pub/sub/ so it is accessible via http://localhost/sub/ for example you have to make sure that all contents of pub go into sub instead. Also you have to change one line of code in tPy.php. If it is in the same directory structure you can simply add another dirname():
// Default tPy_site_dir if turbopy is installed directly "below" the document root so
// http://localhost points directly to the pub folder for example
define('tPy_site_dir', dirname(tPy_pub_dir) . '/');

// Alternative setup if the pub folder is located in a subdirectory, for example http://localhost/sub/
define('tPy_site_dir', dirname(dirname(tPy_pub_dir)) . '/'); 
You can also set an absolute path instead of the dirname fancyness but this usually makes it harder to deploy the website if you change things on your local server. These settings are pretty much defaults and can be fully customized but that depends on what you want to achieve.
HINT: Try to avoid different setups on local and live systems. So if you choose to use TURBOPY in a subfolder on your live system your local development system should reflect this as well. This is the best way to avoid hassle with paths later on.