Are you looking to make a dedicated server or when you are on you want to allow others to join with you. Simplest way is if you are playing single player simply hit escape and click "Open to LAN". This is limited to others only being able to play on the server when you are playing though. For a dedicated server there are many options.
I think the OP just want to know how to export his save "the SSP world" to the server itself.
To do this, shut down the game session and exit the world..
Next go to... C:\Users\your user\where ever you installed FTB at\Mod Pack that your using\minecraft\saves
Then finally just copy the "saves" folder over and rename to "world" without the quotes.
Setup the remaining parts of the as usual and then fire it up.
