documentation isn't really sparse, it only requires a bit of your own research and practice..
Start with following links (preferably in this order) and take a good read:
Windows basics (general tutorial to help you create a window where you can start drawing),
Module 3. of this tutorial also contains Direct2D sample program introduction:
https://docs.microsoft.com/en-us/windows/win32/learnwin32/your-first-windows-program
When done you can start on these 2 links for more info and additional tutorial
Getting started with direct2d:
https://docs.microsoft.com/en-us/windows/win32/direct2d/getting-started-with-direct2d
https://docs.microsoft.com/en-us/windows/win32/direct2d/direct2d-quickstart
At this point you may want to know more about API generics:
https://docs.microsoft.com/en-us/windows/win32/direct2d/the-direct2d-api
next you can take a look at these specific examples:
https://docs.microsoft.com/en-us/windows/win32/direct2d/d2d-samples
This is a good start, and most people started here, what next?
You will for sure want to learn about DirectWrite, a subset of DirectX for working with text,
contains samples, reference etc..:
https://docs.microsoft.com/en-us/windows/win32/directwrite/programming-guide
If you read hard enough from these links, you should be able to continue by browsing reference directly or preferably via google to get to documentation of your interest.
Following links are not related to DirectX but you may want to take a read or use them with DirectX, which you can save to make sure that you don't use/learn deprecated API's in the future (because internet doesn't have many samples about these so you may go wrong route very easy) for
Audio/Video:
https://docs.microsoft.com/en-us/windows/win32/medfound/about-the-media-foundation-sdk
Image manipulation:
https://docs.microsoft.com/en-us/windows/win32/wic/-wic-programming-guide
Note: These link are direct to tutorials because that's what you seem to be looking for, skipping introduction text, you may want to read introduction and other sublinks on these pages later.