What would you like to do with Power BI then?
For data reporting representation purpose, you can start to be familiar the visuals with the mentioned link. A further step, to re-model the dataset, you will have to learn on DAX and PowerQuery(not very necessary) language.
For Power BI integration with your own app, you can start with What can developers do with Power BI, also with What is Microsoft Power BI Embedded. Those two feature do the similar thing, say embedding a report in your application. The mainly difference between them is where you publish the reports, former to Power BI Service(AAD integrated), latter to Azure Workspace.