If you have any question about HTML5 Builder or the RPCL, your first impulse should be the context help. Pressing the F1 key while selecting a component on the Designer or the Tool Palette, a property on the Object Inspector, or even an identifier on the Code Editor, will bring up any help available for the target element.
All over the HTML5 Builder documentation you will find references to help resources for each topic, including tutorials, video tutorials, sample applications, documentation and reference documentation.
For specific questions, you should check the FAQ, as well as the list of frequently encountered problems and solutions. If you still can't find your answer, you will find a friendly user community willing to help you at our forums.