[2020] Can someone explain to me mods and how to get them to spawn in the game? I know have to subscribe to them but from there what?

1. If the mod creator has made it so that they can spawn on the map you're playing on, they'll spawn.

2. If you're playing on a custom map that has manually added spawns for that modded content, they'll spawn.

3. If you downloaded a mod that specifically adds spawn tables for that modded content, they'll spawn (assuming the spawn tables are relevant to whatever map you're playing on).

If it can spawn, the mod author will usually specify so in the mod description.