How would I get mods on mine os running mine os on Ubuntu

I followed downloading mineos through this tutorial : Turn Your Old PC Into a Minecraft Server for FREE with MineOS! - YouTube . I am able to make a vanilla world, and run that perfectly fine, and I am able to access the files of the computer I am hosting mine os from, so I’m pretty sure I don’t need to use sftp, I can just download the mod files and place them in their, although honestly I just want some help of turning the server from a vanilla one into a forge one, and then some help of how I would get executable jar mods into my servers mods