Here's the first video in the series, but do see the links below for the full video set - it's quite extensive and a huge amount of work has gone into it.
Happy painting!
An Overview of the Tools in Paint 3D
-----------------------------------------------------------------------A Guide to Opening and Inserting Content in Paint3D
-----------------------------------------------------------------------A Guide to 2D Selection and Cropping in Paint 3D
-----------------------------------------------------------------------A Guide to Using Magic Select in Paint 3D
-----------------------------------------------------------------------A Guide to Manipulating 3D Objects in Paint 3D
-----------------------------------------------------------------------A Guide to Using 3D View Mode in Paint 3D
-----------------------------------------------------------------------A Guide to the Using the Brushes, Colours and Materials in Paint 3D
-----------------------------------------------------------------------A Guide to Using 2D Shapes in Paint 3D
-----------------------------------------------------------------------A Guide to Using 3D Shapes in Paint 3D
-----------------------------------------------------------------------A Guide to Stickers and Textures in Paint 3D
-----------------------------------------------------------------------A Guide to the Text Tools in Paint 3D
-----------------------------------------------------------------------A Guide to the Effects in Paint 3D
-----------------------------------------------------------------------A Guide to the Canvas in Paint 3D
-----------------------------------------------------------------------A Guide to Using the 3D Library within Paint 3D
-----------------------------------------------------------------------A Guide to Uploading Models to Remix 3D
-----------------------------------------------------------------------A Guide to Saving and Sharing in Paint 3D
-----------------------------------------------------------------------As someone who has done a fair number of voice-over tutorials in their time, I can only emphasise that getting audio and video to sync up perfectly is a lot of work - and Microsoft has done a cracking job here. If you watch all the videos above then you're halfway to becoming a Paint 3D expert.
PS. If you also occasionally hanker for the older, simpler, Paint, then 'Classic Microsoft Paint' should already be on your Windows PC. In the search box next to Start on the taskbar, type 'paint' and then select it from the list of results.