Apart from the official Kicad documentation, there are many resources available on the internet showing how to use Kicad. Unfortunately, the quality is variable and significantly, many of the tutorials do not show which version is being used. There have been many changes between V4 and V5 and even between 5.0 and 5.1 I am starting a list here of unofficial and unsupported tutorials as a starting point. Please add/amend as you see fit. These do not have any official endorsement but are provided as points of reference.
https://techexplorations.com/st/klp_2e/# Kicad Like a Pro, 2nd edition
A new book for the world’s favourite open source printed circuit board design software. Focusing on V5
The KiCad Digikey library and links to a series of 17 videos by Shawn Hymel outlining the complete Kicad workflow, including the differences between V4 and V5.
A comprehensive run though the KiCad workflow. Well written but for KiCad 4.0.6 so now rather out of date.
A tutorial showing complete ARM board development in KiCad 5.0.2. Includes some mechanical layout in OpenSCAD.
A quick run through but now rather out of date - using KiCad 4.0.x
https://m.youtube.com/playlist?list=PLy2022BX6EsphFLOoGI_fQRpew1i28Y02 An series of videos and updates on KiCad 5 and 5.1 from @ChrisGammell from Contextual Electronics
An in depth, 32 part, detailed video tutorial concentrating on KiCad 5.