You want to set the title of your graph.
An example graph without a title:
library(ggplot2) bp <- ggplot(PlantGrowth, aes(x=group, y=weight)) + geom_boxplot() bp
With a title:
bp + ggtitle("Plant growth") ## Equivalent to # bp + labs(title="Plant growth") # If the title is long, it can be split into multiple lines with \n bp + ggtitle("Plant growth with\ndifferent treatments") # Reduce line spacing and use bold text bp + ggtitle("Plant growth with\ndifferent treatments") + theme(plot.title = element_text(lineheight=.8, face="bold"))