Click the 'Installer' button in the 'Download Latest' section. This will download a JAR file to install Forge on any operating system. The installer will be for the latest release of Minecraft. You can download installers for earlier versions of Minecraft by clicking the version buttons on the Forge website. You can check what version of Minecraft you use by starting Minecraft and looking at the window's title bar.
The version number will be displayed after 'Minecraft.' .
When a new version of Minecraft is released, many mods are not updated as quickly. You may need to run earlier versions of Minecraft to use certain mods. Visit some modding websites. Now that Forge is installed, you can begin downloading some mods. Keep in mind that mods can be fickle, and you may run into problems if you install a lot at once. Try to install one or two mods at a time and then slowly add more as necessary, or use different mods for different games. Below are some of the more popular modding sites:.
http://minecraftsix.com/category/minecraft-mods/.