I've created an NMDS plot using vegan but I'm having trouble adding convex hulls. I need three hulls: one for Decatur (D610F, D15F, D15B, etc.), one for Hickory Road (HR610F, HR15F, HR15B, etc.), and one for Cedartown (C610F, C15F, C15B, etc.). Any help would be greatly appreciated. I'll add the codes I've used below along with a screenshot of my graph. Thank you in advance.

#NMDS analyses

WD <- "C:/Users/jacob/OneDrive/Documents/R/win-library/3.6/vegan/data"

setwd(WD)

require(vegan)

phylum.dat <- read.csv("Phylum data for R.csv", stringsAsFactors = T, header = T, row.names = 1)

diversity(phylum.dat, index = "shannon")

specnumber(phylum.dat) #species number

beta <- vegdist(phylum.dat, "jaccard", binary = TRUE) #jaccard distance

mean(beta)

dist(beta) #distance matrix

NMDS <- metaMDS(beta, distance = "jaccard", k = 2)

plot(NMDS, display = "sites", type = "text") #adds labels to plot