After purchasing the product, download the compressed file that comes with the product. This is a .zip archive. You need a software to extract the files from it. (WinRAR is a good example)
It is compressed to reduce the file size. It doesn't have any other effects.
Then just append the materials, models and sculpts into your blender project and start playing around with them.
Here's a short video on how to append the materials:
Here's another video on using the grass assets:
You might face some issues with micro-polygon displacements as it is still an experimental feature in blender.
So here's a video explaining some of the quick fixes:
- If you want realistic results, make sure the Axis-Selector settings (present in few materials) and Scale are accurate. Play around with them until it looks correct.
- It is also recommended to use HDRI-Lighting to get the most photo-realistic renders.