First login to Radarr/Sonarr and copy the API key from Settings -> General.
When adding Radarr/Sonarr to Prowlarr (Settings -> Apps -> Add) use the following settings after replacing the content in the brackets <>,
Radarr
Prowlarr Server - http://<username>-prowlarr:9696 || Example - http://abcd-prowlarr:9696
Radarr Server - http://<username>-radarr:7878 || Example - http://abcd-radarr:7878
API Key - <paste the one you copied from Radarr>
Sonarr
Prowlarr Server - http://<username>-prowlarr:9696 || Example - http://abcd-prowlarr:9696
Radarr Server - http://<username>-sonarr:8989|| Example - http://abcd-sonarr:8989
API Key - <paste the one you copied from Sonarr>
