fixed TLSSocket documentation error from Issue #3963.

doc/api/tls.md

@@ -876,6 +876,31 @@ socket.on('end', () => {
 });
 ```
 
+When using an instance of `net.Socket`, use `net.Socket` to upgrade an existing socket. 
+Do not wrap the `net.Socket` in a `TLSSocket`. 
+
+See the example below for usage of upgrading an existing socket:
+
+```js
+const { Socket } = require('net');
+const tls = require('tls');
+const sock = new Socket();
+const secureSock = tls.connect({ socket: s }, () => {
+  console.log('The tls socket connected.');
+});
+sock.connect({ port: 6697, host: 'irc.freenode.net' });
+```
+
+If using TLS as the initial default rather than net.Socket, 
+use only `tls.connect()` to upgrade the socket:
+
+```js
+const tls = require('tls');
+const secureSock = tls.connect({ port: 6697, host: 'irc.freenode.net' }, () => {
+  console.log('The tls socket connected.');
+});
+```
+
 ## tls.connect(path[, options][, callback])
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