On Ubuntu 18.04.1, how can I set up and use a Minecraft mod?

I have discovered numerous directions on how to do it online (such as here and here), but either these guidelines are outdated or they are ineffective.

Lucky Blocks is the mod to install, and it appears to only be compatible with version 1.12. As a result, I have a Minecraft Forge Server 1.12 already installed.

Then what? The mod file should be put into the mod folder, according to the instruction. However, such a folder does not exist in either the client (in /.minecraft) nor the folder where I downloaded the forge version (in /.minecraftForge12). then produce one? Where? Who is the server? Then, just how do I utilize this mod?

Additionally, I want users from other servers to be able to connect to this modded Minecraft server. Do they have to put something in place? What? Where?

These are the actions I took:

on the machine, forge server 12.2

  1. created a modifications folder on the computer's forge server 12.2
  2. inserted the mod zip file into the modifications folder of the computer's forge server 12.2
  3. Starting the standard Minecraft client. There are no available mods.