As you already used wizard to make some primary configuration, you can continue with using of few another wizards to finish complete setup of your company. You can find a small Assisted Setup to see what you need to finish.

When you open a Migrate Business Data, you will continue with the wizard. And first, you can see what extensions you already have. Yes, you hear fine; you can use different extensions as apps. By default, you have three of them: Envestnet Yodlee Bank Feeds, PayPal Payments Standard and QuickBooks Data Migration (just click on Open Extension Management and you will see). It looks fine:

Then, you can choose to import from Excel or from QuickBooks (because you have an extension). Than, you can download all templates and fill them. When you fill them, you need to configure Settings to set default templates and import this Excel file after that.

You will see the numbers of your main data (Customers, Vendors and Items) and if this is correct, just apply them. If you have errors, you can see them with all details. On the end, you need to finish process and import is completed.

It is easy, but I think it will not be possible to be finished without some support from partners. Client without standard NAV knowledge will not be in situation to import and configure everything they need. This is still job for partners.