If it's your first time seting up vent, you'll want to click "New" and type in the name of the vent server. It doesn't matter what you call it, it's for your reference only. You could call the Integrity vent "Moladun's Vent" and it will still work.
Enter the hostname/IP address, the Port number and the password. The most up to date vent info is always in the Guild Information window in WoW. The password is case sensitive.
After that, click Ok to go back to the main screen, then "Connect" to connect to the server.