FactorioGuideDrop the mod's zip, named exactly name_version.zip as it came from the mod portal, into /factorio/mods/ with the Files card or SFTP and restart. Factorio…
Drop the mod's zip, named exactly name_version.zip as it came from the mod portal, into /factorio/mods/ with the Files card or SFTP and restart. Factorio finds it on startup and turns it on. Your uploaded zips, and a mod-settings.dat you put there, are kept across restarts, server moves and backups, even when you upload them while the server is stopped, and the Mods card never touches them.
Do not unzip it. Upload the file as downloaded into /factorio/mods/. Keep the original name_version.zip filename: Factorio matches it against the mod's own metadata, and a renamed zip stops the whole server from starting. The dashboard then tells you which file to rename and the name Factorio expects. That is a Factorio rule, not something we control.
Restart your server. On the next start Factorio discovers the zip and switches it on.

Your players will see the mod list when connecting. If Factorio refuses a mod, the server does not start and the dashboard names the mod; the Console card shows why, for example a mod it needs that is not installed, or a version made for another Factorio release. Upload the mods it needs the same way, or pick a release made for the Factorio version your server runs.
Players get mods automatically only when joining through Factorio's sync prompt. When a player joins, Factorio offers to sync mods with the server; they accept and it downloads what is missing. Nintendo Switch players can only join servers without mods.
Mods that need Space Age only start when your server's Space Age DLC setting is on, and a mod that does not work with Space Age needs it off. Changing that setting keeps your world: turning it on adds Space Age to it, and turning it off removes everything Space Age added (Haptic saves a backup first).
Mod settings: put your mod-settings.dat in /factorio/mods/ too. It is kept like your zips.
Big overhaul packs need memory. If the server gets sluggish after a large pack, see Understanding your memory budget.
Removing a mod: delete the zip from /factorio/mods/ and restart. Anything installed from the Mods card is managed there (including the mods it needs, which it adds for you); remove it on the card instead.
Ask on Discord or email support@haptic.gg with the mod name and the first error lines from the Console card.