The smallest number in the list is 14 and the largest is 27 

14 occurs 1 time, so the frequency of 14 is 1
15 occurs 3 times, so the frequency of 15 is 3
16 occurs 7 times, so the frequency of 16 is 7
17 occurs 5 times, so the frequency of 17 is 5
18 occurs 1 time, so the frequency of 18 is 1
19 occurs 2 times, so the frequency of 19 is 2
20 occurs 0 times, so the frequency of 20 is 0
21 occurs 1 time, so the frequency of 21 is 1
22 occurs 1 time, so the frequency of 22 is 1
23 occurs 0 times, so the frequency of 23 is 0
24 occurs 0 times, so the frequency of 24 is 0
25 occurs 1 time, so the frequency of 25 is 1
26 occurs 2 times, so the frequency of 26 is 2
27 occurs 1 time, so the frequency of 27 is 1

We start out with a graph marked
as follows:



Now since 14 occurs 1 time, we draw
a rectangle with height 1, whose base
starts at 13.5 (.5 below 14) and ends
at 14.5 (.5 above 14)



Now since 15 occurs 3 times, we draw
a rectangle with height 3, whose base
starts at 14.5 (.5 below 15) and ends
at 15.5 (.5 above 15)



Now since 16 occurs 7 times, we draw
a rectangle with height 7, whose base
starts at 15.5 (.5 below 16) and ends
at 16.5 (.5 above 16)



We continue drawing such rectangles,



That's all there is to it.

Edwin