How do you install mods for Stardew Valley?

lots of mods don't work on their own, they need Content Patcher installed too. it's just another mod and goes in the same Mods folder. if something isn't showing up in game, read the SMAPI console window when it starts. it names the mod that failed and what it's missing, which is quicker than guessing.

yes, SMAPI first. Run its installer, point it at your game folder, and from then on you start the game through SMAPI (on steam it can set itself as the launch option). mods just get unzipped into the Mods folder in the game directory, each in its own folder. on removing: pure QoL mods (UI tweaks, lookup anything, chest stuff) you can pull out whenever. the risky ones are mods that add items, crops, NPCs or buildings, since your save can end up holding things that no longer exist. either way back up the save folder before you start, it's in %appdata%\StardewValley\Saves.