The CIM Skype for Business tutorial video is a 5-minute long video that covers the basics of using Skype for Business within CIM and shows you most of what you should need to know. The tutorial video is located here: https://web.microsoftstream.com/video/91cfc3c1-c641-464f-920a-b966d048f848
The Office 365 Skype for Business Training Center has bite-sized videos showcasing how to do certain things within Skype for Business. This may be more useful if you're looking for a walkthrough on something specific. The Skype for Business training centre is located here: https://support.office.com/en-us/article/video-what-is-skype-for-business-3a21eca4-434d-41f1-ab06-3d4a268573b7