In this example I will use the [BR-DISK](/Radarr/Radarr-collection-of-custom-formats/#br-disk){:target="_blank" rel="noopener noreferrer"} Custom Format, the one most people don't want to download anyway. And if you do, then you probably don't use Radarr or Plex, being both don't support it.
Visit the [Collection of Custom Formats](/Radarr/Radarr-collection-of-custom-formats/){:target="_blank" rel="noopener noreferrer"} and select [BR-DISK](/Radarr/Radarr-collection-of-custom-formats/#br-disk){:target="_blank" rel="noopener noreferrer"} from the table.
Paste the `JSON` in the empty `Custom Format JSON` box (1) that you got from the [Custom Format Collection](/Radarr/Radarr-collection-of-custom-formats/){:target="_blank" rel="noopener noreferrer"} followed by the `Import` button (2).
Personally, I would only add the Custom Formats that do what you actually prefer, especially in the beginning, including the [Releases you should avoid](/Radarr/Radarr-setup-custom-formats/#releases-you-should-avoid)
Check out the [How to setup Custom Formats](/Radarr/Radarr-setup-custom-formats/) where I will explain how to make the most use of custom formats and show some personal examples that I'm using. You can use these examples to get an idea on how to setup yours.