So, you purchased your first Lightroom preset collection. You faithfully follow all the instructions and get the preset collection to show in the Presets panel. However, no matter what you do, you can't get the individual presets in the collection to show.
What is going on? What went wrong? Nothing! You did great and there is only one last step for you to follow: Click the black triangle that is beside the set name.
Many people try to double click on the collection name, and become alarmed when nothing happens. I understand that frustration because on both Macs and PCs we've been trained to "open" folders by double clicking on the folder. So, you would think Adobe would have designed it such that double clicking would open the preset folder. Unfortunately, they did not.
Here is what the Preset panel looks like with preset collections installed but not open.
The next image shows what it looks like when the triangle is clicked.