Click the Apply button with "Run this container.." selected...
Open a browser tab and enter your local NAS_IP and JDownloader port 5800... Like this
192.168.1.10:5800
That's all. Jdownloader should open in your browser window. If it does not, select the container, select Logs and see if there are any errors.
Note: If you use the JDownloader browser extension (myjdownloader), substitute port 3129 for 5800 in your URL.

Open a browser tab and enter your local NAS_IP and JDownloader port 5800... Like this
192.168.1.10:5800
That's all. Jdownloader should open in your browser window. If it does not, select the container, select Logs and see if there are any errors.
Note: If you use the JDownloader browser extension (myjdownloader), substitute port 3129 for 5800 in your URL.