There is a lot of great stuff on YouTube. By the way I find it is even more excellent to watch YouTube with my Roku.
But I digress.
There are a lot of Laura Chappell videos about network troubleshooting with Wireshark.
Much of it is in the Laura's Lab Kit distribution at:
Here is one example of a great video that demonstrates Wireshark features for troubleshooting:
Links to others and my notes from each are available in this document: