When using porndb.me for downloading the hottest adult stuff from usenet, you need an indexer. When you register you get free access to nzbporn.org so you are able to download nzb files right away.
But many usenet porn downloaders have multiple nzb indexer accounts and some of them, the best and most popular can be used with porndb.me to get even more porn releases.
Why does porndb need your api keys to give you access to other indexers? porndb does not intend to steal from other indexers. NZB files are always downloaded directly by your browser from the indexer itself and therefor you need your own api key so that porndb can generate a working link for your nzb download. So porndb does not host any nzb files and they are directly downloaded from the indexer to your desktop.
Retrieving the api key from your indexer is pretty straightforward. You can find it in the settings or profile page when you login with the indexer. It is the same key you need when using programs like sonarr, radarr, nzbhydra and so on.
Some indexers require a second info, the userid to work. This is a bit more tricky. The userid is not the username you registered with, it is the internal number under which the indexer filed your account. If you are familiar with making api request to your indexer you will find the userid in the nzb link. But there is an easier way to get the userid. Here is an example for drunkenslug:
Login to drunkenslug an then goto https://drunkenslug.com/rss
Get the number after &i= and copy that in the userid field on pordb along with your apikey. The api key and userid in the picture above is random and not valid, just for demo purposes.
That see how is is done for nzb.su:
Login to nzb.su and goto https://nzb.su/profile
Goto Site Api/Rss Key and copy the link on the right side. Paste that link in an text editor and extract the userid:
Copy this userid along with the api key in the nzb indexer settings page on porndb. Click save and you are set.
If you want to delete an indexer on porndb simply empty the fields and it is deactivated and is not used in stuff like "My Indexers" in the search filter anymore.