I wrote a quick how to in this post
Just know that it ONLY works for 1.7.10.
Or get the Minecraft Cauldron server v1.7.10
I recommend using this server instead, because it can load Crafbukkit plugins and forge mods at the same time.
Make sure to have all models available on the clients that connects or you will not see the other players models. I recommend models with very little physics.