Hi Rick, currently we don't have a thorough tutorial supported, the one we have is the Help site.
In Forms, you can view Reports/Dashboards and edit Reports from either under "My Reports" or "View Metrics" for each process under "Processes". You will be able to create Reports in "View Metrics". For the specific aspects you mentioned above,
1. You can customize Reports by editing an existing Reports from either "My Reports" or "View Metrics". Reports are a collection of instances for this process. The information which you can customize for a report is the same as what type of information you see when creating a report. It includes the name of the report (Report name), who can see the report (Visible to), creating the report with existing report settings (Template) - settings include the "Columns" and "Filters" below, what information about the instance - current step, start date etc. - to show in the reports (Columns), and the filters for some specific items (Filter) - such as current step (which step this instance is on), status (whether this process is running or terminated etc.). These information is what you can customize the reports when creating or editing it.
2. The whole reporting includes dashboards (operational/performance), instances, tasks, and reports. Dashboards demonstrate the statistics for all the instances/tasks for this process. Instances page shows the information about all the instances, including instance history, variables (and variable values). Task page shows the status and information of each task. Reports page is a group of instances that created by the customized information stated in 1.
3. Operational dashboard is showing the statistics of running instances/tasks, while performance dashboard mainly depicts the statistic information for finished instances and completed tasks. For perfomance dashboard, if you configure "Show Items" to be "started" in Edit button on the top right, you will see also pending instances/tasks in the summary.
4. For dashboards, you can specify who can view it by the button on the top right of dashboards page. For reports, as stated in 1, you can specify the viewers by the customize item "Visible to".
Hope this helps, let me know if you have more questions.