It is recommended to add a daily restart to your Ark server as there is a known memory leak, which can slowly consume more and more RAM over time if left unattended, causing the server to run out of memory and crash.
To add mods to your Ark server, simply add the ActiveMods= section to your /home/container/ShooterGame/Saved/Config/LinuxServer/GameUserSettings.ini under the [ServerSettings] section. This is found at the top of the file.
Eg. for Structures+ and Awesome Spyglass
ActiveMods=731604991,1404697612
The server will then automatically download and update the mods in this list on each startup