To install the asset, open the Package Manager and from the drop-down menu select My Assets. Then, search for PIDI Planar Reflections 6. Download the asset and prepare to import it into your project. You will see the screen showing all the contents of the asset (in the following picture we show the contents of the Personal Edition):
If you are using the Universal RP edition of the asset, you can simply import all the contents of the package into your project as there is no content from other pipelines available and the Package Manager will have downloaded the version of the asset that better matches your Unity version. If you are using the Personal Edition, please read the following section.
Personal Edition and multiple rendering pipelines
If you are using the Personal Edition of the asset, remember to deselect all the folders designed for other pipelines to reduce the amount of content installed into your project and avoid any potential errors. Inside the folders for each pipeline you can find several different unitypackage files designed to match different Unity versions. The right order to install these additional Unity packages should always be Source & Shaders -> Additional Resources (such as Amplify Shader Editor Nodes) -> Demos.
Every time you update the asset to a newer version, simply import the most recent unitypackage within the folder that matches the rendering pipeline you are using. We recommend you back up older versions of the asset in case that you want to roll back any upgrade / update.
Upgrading from older versions
If you are upgrading from Version 5.x.x of Planar Reflections you just need to remove it entirely from your project before installing version 6.x.x. Once installed, version 6.x.x will, under normal circumstances, replace all references to the previous version without any issues. There may be some small differences in performance and / or visuals due to several brand new settings and internal changes added for version 6, but these should be minimal and can be tweaked within minutes.