Hi Xiao,
You can create a depth graph from a bam file using IGB Track Operations.
To create a depth graph:
Right-click on the track's label on the left side of IGB (CLIP33BC1_M1T.sorted.bam in your example).
Highlight Track Operations in the right-click menu and select Depth Graph (All).
This will create a new track with the depth graph information.
Let me know if this helps or if you have any other questions!
Best,
Nowlan