Make sure that the directories used by TinyBoard are writable. Depending on your setup, you may need to chmod the directories to 777.
The default directories are:
./res
./src
./thumb
./
Ensure everything is okay by running test.php in a browser. The script will try and help you correct your errors.
Run the post.php script. It should create an index.html and redirect you to it if everything is okay.