library(ggplot2)
library(rgdal)
library(sp)

smap1 <- readOGR("C:/Users/idan.benaun/Downloads/NGA_adm_shp/NGA_adm1.shp")
smap1_df <- fortify(smap1, region = "NAME_1")
idList <- smap1@data$NAME_1
center.df <- as.data.frame(coordinates(smap1))
names(center.df) <- c("long", "lati")
fin.df <- data.frame(id = idList, center.df)

ggplot()+
  theme_void()+
  geom_polygon(data = smap1_df, aes(x = long, y = lat, group = group, fill = id), color = "white") +
  coord_map()+
  geom_text(aes(label = id, x = long, y = lati), data = fin.df)