Gallery example only gives access to .pro file

Qt 5.15.0 install

Reading about QML and C++ integration (my browser)
I came across a reference to an example
"Building and Running an Example". I noted an example
named "gallery" I used Qt Creator/Examples and located
the Example. When clicking on it, The example was added
to my projects. However, the build button was not activated.
It only reference the ".pro" file. (see snapshot for project
and .pro file.