Try the other sample PDF files. Once you’re confident running the example PDF files, run your own test files.
The Harlequin Core has very rich and flexible controls for use in a wide variety of use cases. That richness, however, can make it difficult to find the right information to allow you to make it do what you need it to do. Please see Hqn100 - Guide to Harlequin Core Resources 13.0r1 which provides pointers to help you find the right resources.