Yesterday, I tried my first customization for existing Report. I can't find any training resource on Microsoft Learning Portal. So, this is the way I tried by myself.
Scenario:Customize an existing report on Dynamics 365. For example, Dimension Statement in General Ledger module.
Create Model:Once you know which report will be customized and search for all related object. Notice that those objects are under "Application Suite".
When create a model about report, we must select the option "Select existing package" as a part of "ApplicationSuite"