How do you start your own thread?

First off, install a modloader. The most popular one being Forge. Run the Forge profile from your Minecraft launcher and let everything load. Close Minecraft.
If you're on windows follow the following to install mods after installing and running forge.
- Press [Windows Key + R] to bring up the RUN prompt
- type in %appdata% and press enter
- Open your .minecraft folder
- Open your mods folder
- Drag and Drop the mods you want to use into the mods folder

Tip: Sometimes Mod files are in Zips and you have to extract the JAR file from within.

Download the Forge Installer and Run it to install the Forge Profile.
http://files.minecraftforge.net/