The Human Surface Shader is a special shader (compare plugin) for DAZ Studio. You can use this to add particular realism to the human surface of your figure.
If you simply double-click on the !Human Surface Base icon, your current texture will be replaced with a silvery sheen. Here's how to add the Human Surface Shader without losing your intended texture.
Load Victoria 4.2 into your scene in DAZ Studio.
Apply your desired texture preset onto her. This can be any texture and doesn't need to be a special Human Surface Shader. In fact, it shouldn't be.
Now to add the special Human Surface Shader without removing your original texture, do the following.
Select Victoria 4.2 in the Scene Tab (VIEW --> Tabs --> Scene). Select V4.2 in the Surfaces Tab (To find the Surfaces tab you will want to go to the View menu and then highlight Tabs and choose Surfaces). Both of these must be selected before the next step.
Find the icon for the !Human Surface Shader in the Content Tab. In Folder View, you can find it here: STUDIO: Shaders: Omnifreaker: Human Surface: !Human Surface Shader.
Hold down the CONTROL button on your keyboard and double-click the icon (!Human Surface Shader). If this is not done correctly then the surface will just change to white.
A dialogue box will appear. This is a control window for applying the Human Surface Shader. You will see the Options Tab and two dropdown windows. Look at the second one labeled 'Map Settings.'
By default, the 'Map Settings' dropdown will be set to 'Replace.' This is fine if you want a silvery Victoria 4.2. Click on 'Map Settings' and change to 'Ignore.'
Click 'Accept' on the tab and wait for the Human Surface Shader to apply.
You will see that your original texture is now 'combined' with the realistic characteristics of the Human Surface Shader.
There are many more ways you can use this tool in your renders. To learn more about these, see the appropriate documentation (readme or WIKI). Enjoy!