I recommend to first read the User Guide or Help on the application. If I answer the questions, the answers will be reduced to citing the help files for the application, but will not be as complete and consistent.
However, to quickly build and plan a project, without delving into the documentation, you can use three features, which are very useful for beginners.
First: the function of creating a new project, which is available in the “File" menu, fill in the data for the master of the project and click the "Create project" button.
Second: after creating the project activate the "Checklist" function, it is available in the "Diagram" menu and on the toolbar, the Inspector will show a sequential list of what needs to be done to build a quality diagram and plan your project, just follow it, marking the execution step by step.
Third: if the previous functions do not suit you, activate the function "Analyze the diagram as a project", it is also available in the "Diagram" menu and on the toolbar. This function will place the recommendations in the diagram, after the execution of which and restarting the function, the planned schedule will be built and the critical path will be found in the project.
Fourth: you can plan a schedule by yourself, but to do that, you have to read the Guide.
I hope that these tips will be enough, but if not, I will be happy to give more detailed recommendations.