Go to the above coordinates.
You will be in front of a webcam that takes a picture every few minutes.
picture: Santa Cruz @ webcam.travel
Now you need someone to save the picture of yourself taken by the webcam or save it as a screenshot on your smartphone.
To log this cache, you have to post this picture.
The picture should allow to identify you as a geocacher.
How you do that is up to you, if you want:
holding up an umbrella, banners, warning vests, balloons, headlights, or cheering into the camera... all the purpose is welcome!