Docker and Jdownloader

[Pietrogramma]

Hi everybody, I'm italian and I'm totally new in the NAS world and linux world. I used a little Docker with OpenMediaVault installed on Raspberry 4.
I buyed from few days, the Terramaster F2-210 and I would like install Jdownloader to download some video from youtube (with Jdownloader for PC it's simply...paste the link and Jdownloader begin the download of the video).
Can you explain me how I must procede for install Jdownloader (or any other contenitor) in Docker?
Thanks and regards