There're several built-in trains and signs in this mod. For many people, it's enough, but for some special users, such as servers, open saves, or restore reality, it's usually not enough.

For solving this, MTR starts supporting custom resources at beta-5. Up to now, it supports to add new trains and signs. Besides, you can also moderate something like decoration blocks in vanilla way.

Many of additions are packed in ZIP format. You can just put it into the .minecraft/resourcepacks folder, open the game, enable it, and use it like using builtins.

Some additions doesn't pack in this format. For these cases, you should open the file and find if there's ZIP files in it. If you directly find pack.mcmeta in pack, you should decompress it into a folder in resourcepacks folder.

For other questions about using a resourcepack, see Minecraft Wiki for more information.

See Make an addition