For the full instructions on how to use, go to:
https://help.poliigon.com/en/articles/6342599-poliigon-blender-addon

For the latest changelog and primary download, go to:
https://poliigon.com/blender

For Blender 4.2 and later:

Step 1: Download the zip file to anywhere on your hard drive, do not unzip it.
        If you are reading these instructions, you likely need to re-download
        after turning off "auto-open files" on your browser!
Step 2: Open a new instance of Blender
Step 3: Drag and drop the zip file anywhere into the Blender window to get a popup
Step 4: Make sure "Enable on install" (and "overwrite", if this is a re-install)
        are ticked, then press Ok
Step 5: Close user preferences
Step 6: Go to the 3D editor, press "n" or otherwise open the toolshelf,
        click on the "Poliigon" tab

For Blender 4.1 and older, or if you have issues with the drag-install above:

Step 1: Download the zip file to anywhere on your hard drive, do not unzip it.
        If you are reading these instructions, you likely need to re-download
        after turning off "auto-open files" on your browser!
Step 2: Open a new instance of Blender
Step 3: Go to File>User Preferences then Addons
Step 4: At the bottom, click Install from File
Step 5: Locate the zipped download and double click it to install.
Step 6: Search for "poliigon" if the add-on does not immediately appear, and
        click the tick box to enable the add-on
Step 7: Press "save preferences” from the bottom left menu in the preferences
        screen, to ensure the addons remains enabled
Step 8: Close user preferences
Step 9: Go to the 3D editor, press "n" or otherwise open the toolshelf,
        click on the "Poliigon" tab

Need further help? You can start a conversation with the team here:
https://help.poliigon.com/en/articles/6342599-poliigon-blender-addon