If you installed Votifier on your server, you will get a public key (it is in the Votifier folder on your server).
That key is what you use on Server Lists (Edit your server on those lists and add the Votifier Public Key) - After that you can ask players to visit your listing on the server list and vote. After they vote, Votifier will contact your server and depending on how you setup Votifier and Listeners, it will award the player.