How to send an object inside an object in postman

Question

const mongoose = require("mongoose")
const Schema = mongoose.Schema
const MonstruoSchema =  Schema ({
 name:String,
      item:[{
         arma:String
       }]
  })
module.exports = mongoose.model ("Monstruo",MonstruoSchema);

which is a "Monstruo" object that contains an array of items called "arma", my intention is to have a monster which can have a list of n weapons.

https://i.stack.imgur.com/tyWWH.png

I am trying to add a "arma" through postman as follows but I have not been able to get the item to add as intended

app.post("/api/monstruo",(req,res) => {
let monstruo = new Monstruo()

monstruo.name = req.body.name
monstruo.item.nombre= req.body.nombre

monstruo.save((err,monstruoGuardado)=>{ 
  if (err) res.status(500).send("no se guardo bienn")
  res.status(200).send({monstruo:monstruoGuardado})
  })
 })