1. Depending on your OS, choose the "ServerStart.sh" for linux or "ServerStart.bat" for windows to start file.
2. For the first startup, you have to agree to the Mojang EULA. Open eula.txt file, read EULA and change "false" to "true" if you accept it.
  ➥ For the world gen, the level-type setting in server.properties must be set to biomesoplenty or terraforged (do this before starting the server)
3. Configure the server in any way you want and have fun!

PS: Don't worry about the red cross before you connect to the server it comes from the forge, but the server works perfectly :)