I bought my first NAS. Complete beginner needs help understanding the process.

Hello there! First of all, thank you in advance. I guess I need to be explained this stuff like I'm an idiot. I bought a DXP2800, added a 8Tb HDD for content and a 256Gb SSD for apps (can't invest more right now, I will eventually). I don't want to get super complicated with it, my friend a I just want a media server to watch movies and listen to music, that's it. I plan to install Jellyfin for movies/series and Navidrome for music. The "problem" is that I've been recommended to use Docker. I don't really u