In the upper corner of the website, click on the Menu and you will see a link to vote for Witness.
Scroll down till you see a field to enter a steem account. In this case, simply type YEHEY then vote. That's it.

Or simply use the link provided below.
https://on.king.net/witness to vote for Witness. You need to login to authenticate and to vote.

Thank you for your support.