About put watermark

We have a docker installation of openvidu app, and I read documentation for trying to apply gdkpixbufoverlay filter to show an image in video conference box.
I found an example to do it, for example gdkpixbufoverlay location=/images/img.png offset-x=10 offset-y=10 overlay-height=200 overlay-width=200 and I have two questions about this.
The first question, where is the location, because it seems to be applied to Kurento Media Sever to write this code?
The second one, is about use the second step in OpenVidu Docs, PublisherProperties in filterEntrypoint of OpenVidu Browser, I hope we need to install OpenVidu Browser which is another application, is it right?
Thanks you!
Kind regards.

Take a look to this tutorial: