Depends on what kind of mods you're using, and for what console you are using them with.
go in to mod folder and click on start
mods are added to the game by:1 downloading them,2 extracting the files (if it's a zip or RAR file),3 putting the extracted folder in the game folder: Frets on Fire/data/mods. you can activate the mods if you start the game and go to options, game settings, mod settings, here you activate it and the mod should be working.
You have to link them using wire, including a lever or switch to activate them.
Well the only viable method I know is Nadi Lai's game mods. This of course costs 10$ to activate. You the get mod points which you can use to spend on game mods.
You should download the mod that you want like christmass mods or else.
Thorium mod, Calamity mod, Exodus mod, Fargo's mod, GRealm mod, Sacred tools mod, Spirit mod, and Temor mod.
Terraria happened in 2011.
Search "Terraria invedit" on youtube.
Just Google Terraria servers and copy the ip address into the multiplayer slot on terraria.
If you have Terraria on Steam it updates itself once an update is available.
Terraria is a one-time purchase. There are no additional fees or payments.