NinjaTrader offers quite a few videos that show how to use their platform. Here’s a link that will bring you to at least some of them. Click on a topic and you’ll see that several videos are available for each topic.
Click the link below for the NinjaTrader 8 Video Library
https://ninjatrader.com/support/helpGuides/nt8/?video_library.htm
Click the link below for the NinjaTrader 7 Video Library
https://ninjatrader.com/support/helpGuides/nt7/?video_library.htm