Girildo

Hello everyone, I am new here and relatively new to minecraft modding. I've looked for this information everyone, but I couldn't find it anywhere, so I decided to ask it here. I am trying to install other mods into the development environment, I put then the .jar files in forge/mcp/jars/mods, but as I want to run Minecraft from Eclipse it show a black screen and the console outputs "Exception in thread "Minecraft main thread" java.lang.NoClassDefFoundError". I'd like to install other mods because I want to use items added by other mods in mine, but the wiki page is actually pretty incomplete, as the spoiler says. Thanks in advance. Girildo.