We cannot provide code to solve your problem, but there are many ways to annotate plots in matplotlib
(which I will assume you are using) as shown here
https://matplotlib.org/gallery/text_labels_and_annotations/annotation_demo.html#sphx-glr-gallery-text-labels-and-annotations-annotation-demo-py
Where a basic example is:
ax.annotate('straight',
xy=(0, 1), xycoords='data',
xytext=(-50, 30), textcoords='offset points',
arrowprops=dict(arrowstyle="->"))
You will just need to calculate the percentages using a standard count or what you want
/total count of possibilities
formula and then you can plot the results using the same x,y as you used to create the bar graph, and include a string with the percentage you just calculated (replacing 'straight' in the example above). This question also does not have a direct answer because you may want to annotate slightly off your bars which will be different than plotting exactly on your bars...