Download the holepunch client, punch and start having fun.
On OSX and Linux you unzip the executable with the following command. On windows, just double click it.
$ unzip /path/to/punch.zip
Note, the actual downloaded filename will be something like punch-linux-amd64.zip
Running this command will log you into your account and guide you through any additional setup required.
$ ./punch setup
To start a HTTP tunnel on port 80, run this next:
$ ./punch http 80