RVT is disabled by default, but is a powerful addition to landscape materials. To enable it correctly you will need to activate it within your project settings first.
Search for "Virtual Texture"
Once enabled in the project settings and the engine has been restarted, enable "Use Runtime Virtual Texture" within the "Runtime Virtual Texturing" dropdown under the "Landscape Material Parameters" drop down.
By default the "Runtime Virtual Texture Sample" has the input of a "RVT_Global" provided by the plugin.
If you want displacement on your RVT landscape and do not want to use UE4's Virtual Height Field Mesh, with tessellation enabled you will want to enable "Displacement Use Mask Sample"
Tessellation and Virtual Height Field Mesh
Tessellation has now been deprecated in UE4.26+ but is still useable at the moment.
Recommended: By default the plugin is setup and optimized to use Virtual Height Field Mesh.
Navigate to the "Tessellation" drop down under the "Landscape Material Parameters" drop down and select which tessellation mode to use.
With "Use Adaptive Tessellation" disabled, tessellation will use a sphere mask around the player camera to determine how tessellated the landscape is. Use the parameters "Range Radius, Range Hardness, Minimum Levels, Maximum Levels" to change how the tessellation is calculated.
This functionality is used to overlay a satellite map over the entire landscape which will fade in at a set distance away from the camera, it is basically another global blend but for the entire landscape.
When applying a satellite overlay, the "Landscape Resolution" parameter needs to be set to the correct resolution of the landscape. You can do this by viewing the details panel of the landscape actor.