How will you find the average velocity between two points on the displacement time graph?

The average slope between two points will give you the average velocity i believe. 

Choose any two points on the displacement time graph.

1st point will have displacement 1 and time 1
2nd point will have displacement 2 and time 2

Change in displacement rate = displacement 2 - displacement1
Change in time = time 2 - time 1

Average velocity = change in displacement rate / change in time
_
v = Δr / Δt