TestComplete samples (both built-in and additional) are located in the <Users>\Public\Public Documents\TestComplete 15 Samples folder.
Some file managers display the Public Documents folder as Documents.
Common samples demonstrate basic techniques of using the TestComplete platform.
These samples are part of the additional sample package. To use them, download this package from https://support.smartbear.com/testcomplete/downloads/samples/ and install it.
After the installation is over, you can find the samples in the <TestComplete 15 Samples>\Common folder.