truffle.js

var secrets = require("./secrets.json");
var HDWalletProvider = require("truffle-hdwallet-provider");
var Web3 = require('web3');
var web3 = new Web3(Web3.givenProvider || "ws://localhost:8545");

module.exports = {
  // See <http://truffleframework.com/docs/advanced/configuration>
  // to customize your Truffle configuration!
  networks: {
   development: {
      host: "127.0.0.1",
      port: 8545,
      network_id: "*", // Match any network id
      gas: 3000000,
      gasLimit: 46000000
   },
   ropsten: {
      provider: new HDWalletProvider(secrets.mnemonic, "https://ropsten.infura.io/"),
      network_id: "*",
      gas: 1000000,
      gasLimit: 67000000,
      gasPrice: web3.utils.toWei("20", "gwei")
   },
   mainnet: {
      provider: new HDWalletProvider(secrets.mnemonic, "https://mainnet.infura.io/"),
      network_id: 1,
      gas: 1000000,
      gasLimit: 67000000
   } 
  }
};

truffle migrate --network ropsten

npm install truffle-hdwallet-provider

secrets.json:

{
    "mnemonic": "your twelve words here"
}