Add text in plot R

I want to add information data in my plot, but it doesn't display the text.

I tried:

warna <- brewer.pal(n = 11, name = "RdYlGn")
warna <- rev(warna)
plot(pm10_mean, col=palette(warna), main="Rata Rata PM10")
plot(shp, xlim=xlim, ylim=ylim, add=TRUE)
text(x,y,"sulawesi")

it just display like this without text "sulawesi"

The plot that i want to save:

Any suggestion to get plot like that?