Update how-to-create-a-HTTPS-server.md (nodejs#2203)

In accordance with issue nodejs#1977, I have updated the Article how-to-access-query-string-parameters with the following changes:

1. Used const instead of var.
2. Removed unnecessary server variable.
3. Added a note on how to execute the program.

locale/en/knowledge/HTTP/servers/how-to-create-a-HTTPS-server.md

@@ -23,23 +23,25 @@ To generate a self-signed certificate, run the following in your shell:
     openssl x509 -req -days 9999 -in csr.pem -signkey key.pem -out cert.pem
     rm csr.pem
 
-This should leave you with two files, `cert.pem` (the certificate) and `key.pem` (the private key). This is all you need for a SSL connection. So now you set up a quick hello world example (the biggest difference between https and [http](/how-do-i-create-a-http-server) is the `options` parameter):
+This should leave you with two files, `cert.pem` (the certificate) and `key.pem` (the private key). Put these files in the same directory as your Node.js server file. This is all you need for a SSL connection. So now you set up a quick hello world example (the biggest difference between https and [http](/how-do-i-create-a-http-server) is the `options` parameter):
 
-    var https = require('https');
-    var fs = require('fs');
+    const https = require('https');
+    const fs = require('fs');
 
-    var options = {
+    const options = {
       key: fs.readFileSync('key.pem'),
       cert: fs.readFileSync('cert.pem')
     };
 
-    var a = https.createServer(options, function (req, res) {
+    https.createServer(options, function (req, res) {
       res.writeHead(200);
       res.end("hello world\n");
     }).listen(8000);
 
 NODE PRO TIP: Note `fs.readFileSync` - unlike `fs.readFile`, `fs.readFileSync` will block the entire process until it completes.  In situations like this - loading vital configuration data - the `sync` functions are okay.  In a busy server, however, using a synchronous function during a request will force the server to deal with the requests one by one!
 
+> To start your https server, run `node app.js` (here, app.js is name of the file) on the terminal.
+
 Now that your server is set up and started, you should be able to get the file with curl:
 
     curl -k https://localhost:8000