Make sure you have the latest pixelmon mod version and the version of forge with that if you need any other help message me on my website www.jcraftpixelmon.enjin.com
1.The Latest Version of Forge Mod Loader
Download the installer, Double click the Jar File and install the client version.
2.The Latest Pixelmon Mod
If you need a tutorial to help you install the Pixelmon mod it can be found here -
Download the Pixelmon mod and save it on your desktop.
Next go to your Start menu and type in the search bar %appdata% and click on the roaming folder.
Open the .minecraft folder and extract the folders from the Pixelmon mod into the .minecraft folder.
Run Minecraft with forge and check to see if it is running Pixelmon.
If you need any more help add the Owner on skype jcraft.support