This was easier to find that I thought. First of all there is just one site where you need to look for everything regardings skins, UIs and LUA stuff: www.lotrointerface.com
The skin that you are looking for is the famous Azure Glass skin.
But the screens that you saw in the tutorial link that you posted are from a very old Version of LOTRO … like around Mirkwood I guess. That means this skin like in the link you gave is not available for the new LOTRO.
But you can be happy. There are a couple of guys out there that took the original Skin from Enfield of Landroval and updated it constantly. And there actually is a version for Riders of Rohan already. Go here and learn how to download, install and use it properly:
(You will need to do a little reading in that post but it's really not so tough and you will get used to how it works pretty fast. And if not - lotrointerface.com is a kinda nice and helpful community. Just ask a question under the actual post and you will get help and replies.)