I have used a Kruskal-Wallis test to analyse my data (as it was not normally distributed), followed by a Dunn's post-hoc test to identify significant differences between groups. I'd like to indicate these differences on the attached plot but can't seem to find a way to get this to work. I have attached a copy of the boxplot and my code if anyone could help point me in the right direction I would be incredibly appreciative as it's safe to say R is not my area of expertise.

# Import dataset: File > Import dataset > From excel... > HCOES

# examine structure of the data

str (HCOES)

# Plot data

library(ggplot2)

p