TextTest can be configured to test anything that is an executable program. Usually you want to store the tests in the same repository as the sourcecode, in a separate folder. This starter project shows a typical layout for an application written in C. Adapt it for your programming language and preferred layout.
To start the TextTest interactive test management application for this application, use Bash or PowerShell or another suitable command line. Change directory to 'test' then run the 'start_texttest' script appropriate for your platform.
The environment variable $TEXTTEST_ROOT is set to the location of your config file so you can use it to define the relative location of the executable program.